Well this is taken from my experience driving a manual for the past 10 years. Think of it this way, its always easier to replace the brakes instead of having to replace the tranny or clutch. (when it comes to downshifting)
as far as your question is concerned, lets say you are in 3rd gear and you see a stop sign approaching from a ways off. According to the manual (pa) you should downshift to reduce your speed, so clutch in, brake, shift to 2nd, let clutch out. (you want to be in or around the speed of 2nd otherwise you are going to lurch forward - if you're going to fast) rinse and repeat for 1st, by that time you should be in front of the stop sign.
but don't quote me, like I said this is all from car experience - NOT motorcycle (im going for my permit today)