Choose a piece for the recital. It should be a composition that is within your reach musically so that you will not become frustrated, and should also be something that you like so that you'll enjoy the process of learning it.
Set aside a practice time every day. Make sure it's during a time frame that will not interfere with other activities because that will make it easy to rationalize skipping a practice session. Even if you cannot spend the allotted time some days, take the time to run through the piece to keep it fresh in your mind.
Practice the piece at a tempo that allows you to play each note with precision. When you reach difficult spots in the music take time to practice those separately and slowly until you have mastered them. Record your performance and listen to your rendition so that you can pick out the trouble spots.
Practice your piece on the instrument that you'll be using for your recital. Although the basic make-up of the piano is the same you must allow for the psychological effects of performing on an unfamiliar instrument in an unfamiliar environment. Make sure the seating is comfortable--not to high or low, or different than what you are used to--such as a round stool as opposed to a bench.
Approach the piano with confidence when it's time to perform you recital piece. If you know that you have prepared to the best of your abilities you will be confident that you'll play well. Remember that the audience is not a jury; they are there to enjoy your piece and wish you the best. Even the best performers make mistakes: if you fumble, continue on with confidence.