Descent planning. LVL CHG and V/S are much easier than VNAV at first.
The 3x table works well, i.e. at FL330 approximately 100nm track miles are required. With 15 track nm to run, you should be reducing to min. clean.
If you are high and have clearance to descend, use LVL CHG and wind the speed up, and think about using speedbrake.
If you are high and ATC aren't clearing you for descent, e.g. you're being kept at FL200, and can't descend lower due to traffic, wind the speed back to 250kt or lower - keeps the trust levers from coming up - adding energy is the last thing you want to do in that situation.
If you're told to descend early, use V/S, set to 500/1000 fpm.
In the descent, update the LEGS pg regularly even if you're given a short cut by way of a radar vector to give a sensible path indication.
As far as landings go, the major difference between light aircraft and B737 is when you take the power off. The power stays on nearly to the ground. The sequence is flare just a bit at 20/25'-ish, then smartly pull the thrust levers to idle at 10'.
In general, don't expect perfection immediately, and expect a few set backs on the way and don't be surprised if the aircraft bites back occasionally.
Hope this is helpful mate.