My wife brought me one home yesterday as an early birthday present. I have never used one. What do I need to know to avoid some of the trial and error phase.

How good and how accurate are they? Thanks in advance for your help.

Works well, accurate within +/- .05grains it seems from my use,  although i haven't weighed charges on an ultra accurate scale to compare. Very infrequently it will overcharge by .1 grain but it will tell you it is over on the screen. I use it for long range ammo and larger rifle calibers and it has treated me well. Don't forget to close the dump spout when you're done or you will spill powder next time. Keep small powders away from the keys and warm it up before using.

Pretty much what LBF says..they work great, I do use a gem. pro 250 to verify every charge, but the lite does very well on its own...

I love mine.  I did the "straw mod" to it (easy search if interested) to pretty much eliminate the very rare overcharge.  I load my 6.5 Creed ammo to sub 5 SD with it.  Be sure to let it warm up at least an hour before use and I generally toss the first couple charges back in the hopper before actually loading cases.  Zero complaints from me.  Sure beats my old ways with the beam scale and powder trickler.