As far as I'm concerned, the question of routining needs to be driven by something. If you have a specific goal in mind - an upcoming performance say - then you need to put together a routine based on what the performance is going to require. However, often this is not the case.
One of the things I noticed when i started performing a lot is that I would always end up doing the same couple of tricks for different audiences, over and over; despite knowing loads of tricks, I would always do the same one or two. After that, if I wanted to carry on, I would relax and start showing other items in my repertoire. I mention this because it made me think about two things:
One - if my knee-jerk reaction is to do these tricks first, I should make sure that they are as good as I can make them. Not only that, but I should build a routine that STARTS with these tricks and progresses from there. This was a major help in creating my first routines, as once you have a starting point you can start to ask questions like "where does this trick leave me when I'm done with it? Could this start another trick? Does my opening trick allow me to get or maintain a setup for my next trick?"
Two - are these the tricks I really want to start with? In other words, maybe you want to change your "go to" tricks before you think too much about routining. If the ones you're currently running to don't necessarily make the best openers, then concentrate on this question first.
The more thought you put into routining, the better your magic hangs together. As an example, 99% of the time I open with a quick, uncomplicated card revelation sequence with a few colour changes and surprises in rapid succession. It lets the audience know that I'm worth watching very quickly, which is important if you want them to pay attention to something a bit more long-winded later on. After that I might do a trick which finds four of a kind, and conclude with four spectators each cutting to that same four of a kind. This routine never fails to get great reactions and mechanically it's very nice - each trick sets up the next. This is an example of "mechanical routining" - using the methodology of each trick as a starting point for the next. John Bannon published a wonderful routine in his book "Dear Mr. Fantasy" which provides a great example of this style of routining.
Another example of routining is to hang each trick on a common theme. I do a "time anomaly" trick - a version of Everywhere and Nowhere by John Guastaferro - which ends in the production of four aces. I then move into a second John G trick called "Jazz Fusion", in which a series of transpositions happen which I present as "jumps back in time" When the trick is almost done, the audience believes that the four kings are face down on the table.
"Actually, I went back in time a little further than you thought - a couple of minutes ago, the cards on the table were aces..."
And of course, they are. Now the tricks have a recipricol relationship that works to strengthen the impact of the whole routine.
Finally, be flexible. Be prepared to change your routines depending on circumstance. Just last week a spectator said "does that mean the kings are back in the deck?" This lead to a quick production of the kings and then off into reset. If you've just finished a trick and a spectator makes a comment about cheating at cards, or "I wouldn't play cards with you!" or something like that, this is the perfect opportunity to dive into a cheating demo - 3 card monte, poker deal, transpositions (with appropriate patter of course). The audience is even more impressed because you are responding to their reactions, which looks more spontaneous.
Zenneth Kok talks about using tricks in pairs - one playing off the other - a "double punch". I like to work this angle rather than think about an extended "routine". I have tricks which work for everybody, tricks which can work for small children, tricks which are more suited to a tough audience, tricks for this, tricks for that...once you read your audience you know what direction to take your act in.
Anyway, hope that's useful to you. best bit of advice really - look at how other, top class magicians structure their routines. David Regal has an excellent series called Premise, Power and Participation which would be well worth your time to study.
Cheers,
David.