for my car, I use 1500 rpm as the optimal shifting point. I then add 5 to 6 hundred rpm's from that point ( approx. at 2000 rpm's ) shift into neutral ,then wait till it falls back to 1500 and it should fall into gear. The more rpm your're at you must wait for a bigger drop in rpm's. Downshifting .... I cheat by adding more rpm ( up to about 2800 I think, partly because I'm usually going a little faster then I should ) and then apply a small amount of pressure on the shifter at the correct gear and it will click in. If you are trying to grab two gears ( from 4th to 2nd, up to 3500 i think ) I go by sound so it's difficult to remember exactly where the rpm's are at. If you here grinding...... I grab the next gear down.
Hope that's not too confusing.