Reading aloud is a skill that either comes naturally or takes a lot of work. Either way, take every opportunity you can to develop your ability to read aloud. Public reading, in places such as school, is one way to acclimate yourself to reading aloud. Interpret the words as best you can. Be loud enough to be heard, and strive to make what you are reading come alive, even if it is boring.
Using recordings is a great way to hear and coach yourself in your reading aloud. Use a digital voice recorder or your camera's microphone or webcam to hear what others hear. Work on pace, timing and inflection until you sound right. Read in front of a mirror to check your expressions and make sure you are not leaving the visual impact out of your reading. Practice reading from scripts. Choose things that express different emotions, and don't shy away from difficult pieces, such as Shakespeare.
Get the lines as early as you can and go over them until you understand every word. Look for clues regarding the character and the context, especially if you don't know the play. What other characters say or how they respond to you are good clues about your character. Working from these, make choices about how you will interact with other actors.
Choose three main traits to present. Make them obvious. Is your character, loud, old, angry, sad? Choose three words to describe her in your head and then act accordingly. Your movement and ability to interact can be limited by holding a script. Develop your ability to give your characters a voice. Not a cartoon voice; think about how they speak. Are they in a hurry to be heard or timid? Remember to speak clearly and loud enough to be understood.
Use the space, other actors and your own abilities to set yourself apart. Make distinctive choices. If everyone is reading the angry king as loud and boisterous, try quiet and menacing. Maybe a shy character is suddenly bold about something that makes him passionate. Bigger choices give you more reaction from other actors and the audience.
Use the space; your feet are not nailed down, so don't act like it. Instead of nervously pacing, think through your actions and move with purpose, then stand, deliver a line or two and move again when it makes sense. Cooperate with the other actors; they are potential teammates. Seeing them as competition to be defeated will not make your performance stronger. If you give them their best audition, it will make you look better.