Depends on your watch.
Invis. Watch: You need to get from Point A to Point B without dropping cloak, since you don't have disguises to fall back on. Know where the ammo is, avoid the front line, grab every dropped weapon you can. Once you're in position, you know what to do.
C&D: Same as always, wait for a straggler and nip 'em.
Dead Ringer: The best for YER if you ask me. You can run around as a revolver Spy for a little while, let yourself get 'killed', then get to your position. If you're lucky you'll soften up or even kill an enemy in the process.