Advice for Students who "Double"
Become a really good player on your first instrument before branching off into others. It doesn't help you to play three or four different instruments if your counting and sight-reading skills aren't their sharpest. Skills like sight-reading and improvising can be learned on any instrument. Once you have learned these skills you can apply them to any instrument you play.
You must fully embrace every instrument that you play. If you claim to play it, you have to practice it. The fingering similarities between sax, clarinet and flute are not enough to get you through. You must develop and maintain a good sound and technique on each instrument. Ditto for Alto and Tenor sax. If you play both, you need to practice both.
Clarinet and Flute can be 'opportunity' instruments: Clarinet is a complicated instrument that is misunderstood by many saxophonists. It can be very difficult to play in some keys, does not overblow in octaves, does not work well with a saxophone embouchure, and is very exacting in terms of fingering technique. This is one reason that it is so highly favored as an instrument to start out on. The flute is a challenging instrument in terms of tone production, and the high octave fingerings can be downright treacherous. As with clarinet, many show gigs demand a 'classical' sound and very solid technique. Most of the parts will be much more difficult than the saxophone parts.
Gigs that I've had with the Richmond Symphony, the Continentals, most of the local theaters, and even my first pro gig as reed player can be credited either directly or indirectly to clarinet skills. There are flute players out there that can tell you similar stories.
Don't be a Gig Pig--share your skills. I can't count the number of guys that have told me, "I only play for pay." A lot of them aren't playing much at all. At some point, you have to decide whether you're a musician or a mercenary. I've had a very satisfying time playing in community groups like the Richmond Pops Band and the Chesterfield Community Band. This gives me the chance to keep my chops up on clarinet and play some different kinds of material. I also get together with friends and play chamber music on flute and clarinet. It's a fun activity that helps keep me in shape, enjoy my friends, and widen my horizons.
NOTE: If you are a professional or a college player sitting in with such groups, try to keep your ego in check. There are many fine amateur players who man these groups, and they are there playing with the community group even when you have to miss their concert in order to fulfill your professional or college obligations. Remember that your presence in such a group benefits you as well as them, and try to focus on being helpful rather than being competitive. Remember that sometimes the only difference between the amateur and the professional is the paycheck.