Best thing so far...be in the correct gear for the speed you're going. Don't pull in the clutch in 5th, then coast forever till you stop, then shift into 1st. Something happens when you're coasting and you need to get on it to get around something or get out of the way of something and you may not have the power/response you need, when you need it. But in the same breath don't have to hit every gear when slowing down either. If you're gradually slowing down over a long distance then you may hit every gear, if you're slowing down rapidly, nothing wrong w/ going from 5th to 3rd, etc...
As for taking off in second from a slow roll, don't lug the engine, learn how to bring the revs up and slip the clutch through the friction zone till you're at the right speed/rpm. I almost never use first unless I'm either at a dead stop or barely, and I mean barely moving.
Engine braking, yeah...I grew up in the dirt so that's a habit I don't think I'll ever fully brake (get it?).