ORIGINAL: bikerboy

When you're accelerating hard (shifting above 6000 rpms) it's actually easier on the clutch and drivetrain to shift clutchless.
You do this by preloading the shifter with your foot as you're rolling on the throttle; when you reach your desired shift point, roll off the throttle slightly, and you will "snick" into the next gear. It takes a little bit of practice, until you get the feel for it. It doesn't take too much pressure to "preload" the shifter, just enough to take the play out of the linkage. And you will get the feel for how much to roll off the throttle to "snick" into the next gear. You can actually shift clutchless through all six gears smoothly, although 2nd tends to wanna pop back into neutral if you don't hit it right.
When you're just cruising easy around town, stop and go traffic, and intersections, go ahead and clutch your shifts--"two fingers" is fine. You don't need to fully disengage the clutch; in fact it's more choppy if you do, and you tend to over rev when you're rolling back on, and it sounds to everyone else like you're slipping your clutch. Just a quick little two finger stab/roll off/click/roll on, and you've got a smooth low rev up shift (3000-5000rpm easy going lazy shift).
When you're doing high speed down shifts, you should blip the throttle to match the engine speed to the next gear down. You do this by clutching (two finger half-stab is fine) and "blipping" the throttle (just a quick little crack of the wrist) as you downshift. When you release the clutch, the engine speed should be matching the gear you just downshifted into, and you will be less likely to have "wheel hop" or the back tire locking up from just pounding the downshift and letting the clutch slow you down.