Learn to stand still.
As a rule, do not speak when you are crossing the stage, but cross first and then speak.
Let the last speaker get his sentence well out before you begin yours.
If you are a comic actor, don't run away with the piece by over-doing your fun. Never spoil another actor's points by trying to make the audience laugh whilst he is speaking. It is inexcusably bad stage-manners.
If the audience applauds, wait till the noise of the clapping is over to finish your speech.
Rehearse without your book in the last rehearsals, so as to get into the way of hearing the prompter, and catching the word from him when your memory fails you.
Practise your part before a looking-glass, and say it out aloud. A part may be pat in your head, and very stiff on your tongue.
The Green-room is generally a scene of great confusion in private theatricals. Besides getting everything belonging to your dress together yourself and in good time, I advise you to have a little hand-basket, such as you may have used at the seaside or in the garden, and into this to put pins, hair-pins, a burnt cork, needles and thread, a pair of scissors, a pencil, your part, and any small things you may require. It is easy to drop them into the basket again. Small things get mislaid under bigger ones when one is dressing in a hurry; and a hero who is flustered by his moustache having fallen under the washstand well out of sight is apt to forget his part when he has found the moustache.
Remember that Right and Left in stage directions mean the right and left hand of the actor as he faces the audience.
I will not burden you with any further advice for yourself, and I will reserve a few hints as to rough and ready scenery, properties, &c., for another letter.