General question about wood painting here:

Does it make a difference if I 1) sand the surface just enough to remove the glossy (either paint or stain; in my current situation I don't know which one it is) 2) strip/sand it to the bare wood, if I'm going to paint it anyway?

And, if I choose to strip it, do I have to get every last bit of whatever it is off?
What's the best stripper? I used up a whole can of spray on a relatively small portion and it didn't all come off.

My questions, for my purposes, will cover furniture, door/window frames, baseboards, etc.

Stripping is only necessary if the origional finish is so bad that its not sticking to the wood. In fact the origional finish makes a good primer for the new finish to adhere to if its in good shape. Just sand real good and get the dust off before the brush hits the trim.

Did you do a lead paint test on the old finish? If not get a test kit at the local hardware store and check before you sand or use any kind of heat gun to remove the old paint. Lead dust and fumes are not something you want to fool around with.

Interesting...I haven't done a test, but for now I'm only doing furniture.

My favorite stripper is the orange gel. It can be messy but works well everywhere I've tried it. Prep is the main thing, but if you don't need to go down to bare wood to get a smooth, even surface then a coat of good primer can cover a lot of sins. Be sure to test for oil-based paint before painting over with latex though. A little Goof-Off, or something similar, on a paper towel will soften the paint if it is latex, but do nothing to oil-based.

Check the furniture as well. Older stuff may very well been painted with this stuff. Old children cribs were painted with lead based paint as I remember a recall several years back once lead was no longer allowed. Do it and be safe.