Apply pieces of masking tape to certain sections of the stage to correctly mark Center Stage (C), Stage Right (R), Stage Left (L), Down Center (DC), Down Right (DR), Down Left (DL), Up Center (UP), Up Right (UR), and Up Left (UL). Use the traditional abbreviations included in the parentheses. Stage directions always follow the actor's point of view. Stage Right is the actor's right. Stage Left is the actor's left. Down Stage (D) is the closest point near the audience.
Stick to the script. Study the playwright's stage directions, both the "directional" ones, such as "She enters stage right," and the "directive" ones, such as this one from O'Neill's "The Emperor Jones": "the expression on his face is fixed and stony, his eyes have an obsessed glare, he moves with a strange deliberation like a sleepwalker or one in a trance."
Rehearse with a director, who can follow the script as you quote the dialogue and coach you if you make a mistake. Quote the dialogue while following the stage directions. Practice quoting the dialogue while moving around on stage, whether you are entering, sitting or jumping up from a chair.