You can improve your acting, dramatically on your own, or with a friend, by doing some simple, easy-to-do-things, and they won't cost you a thing. First and most importantly:
* Consonants - Learn to speak clearly. Practise your consonants. That is the single most important and dramatic way to improve your acting ability. Enunciating clearly does not just reflect the language of newscasters and aristocrats. it allows a person to transcend their local unintelligible dialects. Dropping consonants is a casualty of daily interaction, lazy shorthand with friends, family and colleagues. Consonants give shape to the emotional resonance of vowel sounds. Vowel sounds coming from the actor suggests the feeling inside and consonants let the audience know what that feeling is. Consonants are like the frame of the house. They give it shape. Learn to exaggerate those consonants.
It may sound highly unnatural at first, but after a while, it will become more natural, and will become a ready-to-use and important tool in landing roles. You should practise hitting the consonants in the middle and ends of words. Playing spaces can vary in kindness to the ear. For instance, the sound in the theater might not travel. It might reverberate. It might be perfect. Film, and television can have varying qualities in the sound equipment and sound mix. With certain films at a key point, I've had to play that moment over and over again to make out what the actor said. Be kind to the aging and hearing impaired. Speak clearly. Practice it everyday. Don't think that by dropping consonants you are being real or true to your art. Instead, you are being hard to hire.
* Imagination - Get your imagination in fighting shape. Look at a play and use your imagination to get inside the character's head, inside their heart, inside their soul. Your imagination is a powerful tool we all share. We might be different physically, in looks and talent but we can all harness that power of imagination. If a writer is portraying life on the streets, then use your imagination to find that character within you. If the character is the president of the United States then use your imagination to pick up the ticks and tricks of the trade. Imagination is the single most important tool you have to get inside the head of another character. It is the single most important tool you have to inhabit the world of the play. Having all the talent and the tools in the world will not mean anything if you lack imagination.
Your imagination can only be fed by learning as much as you can about the world around you. Read novels, history, and see films and plays, listen to music and play games. Imagination can take you places where technique and talent can't. It allows you to walk with kings and queens across moonlit desert sands. It allows you to close a drug deal in a back alley. Imagination allows you to breathe life into words on a page and translate them into a living world for the audience to see. Flex the muscles of your imagination, spread your wings and soar above the earth like Oberon and Titania in A Midsummer Night's Dream.
* Projection - You need to be heard. While not so important in film and television, it is important in the theater, and theater is an easily accessible way to get into acting, to acquire the skills needed to succeed in other mediums. Theater is the best way to make connections that can help further your career, so learn to be heard. Don't be shy. It is your right to be heard. Go in a big room, open your mouth and aim your voice at the back wall. Focus on that back wall and your voice will travel there, even in a large room. Use your diaphragm, the muscle under your ribs to push the air and the voice out. Most people speak with shallow breaths. They talk so not to be heard. Talk to be heard. Check out books by Patsy Rodenburg. Her books are goldmines of technique for improving your acting ability with regards to speaking.
* Nouns and Verbs - Nouns are the subject of the sentence. The noun is the thing, the person, or the place that you are talking about in a sentence. The audience needs to know who that person is, where that place is, or what that thing is that you are talking about. Learn to track down the primary nouns and secondary nouns in a sentence.
Say the lines out loud with an emphasis on the nouns. Play with the relative importance of the nouns and pronouns (he, she, him, her, they, you, and so on) Get different meanings out of a line by switching the importance of various nouns and pro nouns. The verb is the active word driving the line to its conclusion. It is essential for an audience to hear what actions are happening in a line. Don't fall in love with pretty descriptions so much that you give adjectives and adverbs precedence over nouns and verbs. Adjectives and Adverbs describe the nouns and verbs. They are less important. Don't make them more so. Let the audience in by letting them know what you are talking about. Nouns and verbs are essential to that communication between performer and audience. If you ignore that, you are going to find it that much tougher to get roles.
* Upward Inflections - This is another important tool for the actor. Many inexperienced actors throw their energy into the beginning of a line, but as they run out of air, the ends of their lines are dropped vocally, which is completely at odds with natural speech. In natural speech, the speaker organizes his thoughts to say that he or she is going to do this, or to go there. What are you going to do? Where are you going to go? These are questions that the last word or two in a line answers. If you pump all your energy, adrenalin and breath into the beginning of your line, then you have nothing left for the end of the line, nothing left with which to answer those questions.
A rush of energy at the beginning of a line, while perhaps exciting for the actor becomes monotonous to the audience. It becomes a predictable succession of vocal peaks and valleys, where the beginning is loud and the end of the line quiet. Do that for too long and the audience will be checking their watches. They won't have a clue what you are saying. Learn where to breathe in your lines, and pay attention to punctuation breaks. Find ways to keep the energy up at the end of a line. Don't plan to leave tired-endings for the other actors to pick up. If you end a line with a word supported by breath, it transfers energy to the next line. It keeps the energy of the play crackling.
* Monologues - A monologue for the purposes of an audition can be a soliloquy, a private speech between actor and audience, or it can be part of a conversation with another character. It should be about two minutes long and be uninterrupted by other characters. Find some monologues that you can use for audition pieces. Look in real plays for these monologues. There are many free monologues on the internet, but many of them are not going to help you land parts. It will probably be useful to have two classical pieces, one comedic and the other dramatic. Shakespeare is usually a good choice because you can find recordings or movies that have those monologues in them. Then you should search for a modern dramatic and comedic monologue. Search for these monologues in highly regarded plays, plays that have been on Broadway for instance or those that have been turned into movies. The reason for that is that you will have better luck researching them and finding recordings for them.
But before you listen to any recordings, or watch any filmed versions, you should do your own work, your own investigation into who the character is and what he is doing, what he is feeling, and what he is thinking, where he has come from and where is he going. The monologue has to travel from the beginning to the end, and you should map whatever change in emotions there might be, when the tempo picks up or slows down. Does the monologue grow in rage? Does it trail off in despair? Find the drama, the irony, the comedy and it's timing. Find the humanity in the piece. You should learn the character inside and out. Learn these monologues so well that you can do them spontaneously. Don't give yourself an excuse for not getting a part with a poorly-prepared audition piece. Blend your thoughts, your emotions into the character's thoughts, emotions and words. Read as much as you can about the character and then listen to a recording or watch a filmed version. You will now understand the character and so hearing or viewing this monologue will give you additional ideas and insight.
* Study other people - Be a student of people. Be a student of people from all walks of life, the rich, the poor, the young and the old. Study their physicality. Watch people walk and listen to them talk. Listen to the rhythms of their speech. Watch people when they sit, when they stand, when they are passionately trying to communicate something or when they seem disinterested, when people are happy, or sad or angry or sleepy. What body language do they use? Imagine what goes on in people's heads. Find two similar looking people and look for clues to their personalities by their posture, by how they move, look for physical clues that might suggest why one ended up one way and one another. How much does nature and nurture have an influence on human beings? Watch what people are doing when they are listening to each other. What do they do with their hands? What do they do with their hands when they speak? Be a student of body language. Shakespeare said that the actor must hold a mirror up to nature. To act, you must reflect what real human beings do. As an actor you are interpreting the human condition, the poetry and music of human emotions, thoughts, actions and communication.
* Read - Read plays, read books about acting, read about famous actors, read acting biographies, read anything. A well-rounded knowledge is essential for an actor. Not only is it important to know about acting, but it is important to know history, religion, psychology, geography, science, so read, read, read. Reading gives you your own credible insight into lines written by playwrights and screenwriters. People who write, read a lot, and to gain insight into these characters, you must read a lot. One casualty of theatre schools is the ability to understand the world. There is not enough contextual knowledge provided in these schools devoted only to acting. Know the world and you will know how to act.
* Get in shape - Treat your body as a temple. Eat right and exercise. Plays and films can be demanding physically. The more you can ask your body to do, the better physically you can fit into a part. If you have a certain physical trait that your character needs, you need to be able to achieve that. Physical activities, like dance, or karate, or running, or yoga, or sports of various kinds can help you prepare physically for demanding roles. There could be dancing, sword-fighting, and other acts of physical exertion needed, while all the while being able to deliver lines supported by breath. Your mind and your body, voice and movement, are the tools of the actors trade. Take care of them.
* The Internet - There is a lot of free information on the Internet. There are many acting tips that are available for free. Arm yourself with as much knowledge as possible. There are a lot of really helpful suggestions for actors out there. Most of the free information is really geared for beginning actors and many of them don't identify technique or different methods in more than a superficial method. But more advanced information can be found in things such as Google Books. The more research you do, the more information you can unlock on the Internet.
Obviously, there are scams out there. There are scams everywhere, and would-be actors are targeted in the real world as well as on the Internet. The more homework you do, the better, and as long as you realize that if you have drive, and are willing to work for what you want, that there are no short-cuts, then you have a good chance for success. But anything you read can only be reinforced by working with others. You cannot act in a vacuum. So to truly succeed you need to be working with other like-minded individuals.