^^This is basically right; you should always open and close on the big numbers.
First, pick a theme. Then, rate all of your effects you might like to perform in a routine out of 5 (and be honest!) based strictly on how entertaining you think they are from a spectator's point of view. Run through all the 5s (there shouldn't be many) and sort them into Openers and Closers; Openers are quick and easy to follow, and very visual, whereas Closers are the other ones. Now, toss out all the effects scoring less than 3. Look at the time each effect takes and how long your routine will be and add up effects that total about 85% of the time you have, e.g. if your routine will be 30 minutes, you'll want about 22 minutes of magic; the other eight minutes will be introducing yourself, patter inbetween effects and impromptu interaction with your audience. Make sure that you have an Opener at the start and a Closer at the beginning. Last thing to do is to script your routine so each effect links with the ones pre and proceeding it and everything you do fits your theme.
I use this method for coming up with bi-monthly stage shows I put on in Leeds. I know I have 20 minutes on stage, so I always account for about 5 minutes of non-magic. I think up a theme and then make the routine fit around it. Recently I performed a stage show based on control and the effects I performed were all about free choice, how free is choice, how controling choice can be and influencing choice. Very entertaining show to perform and all written and rehearsed ready for stage in just over a week (obviously not a good amount of time but notice was very very short).
thanks for that, now i know