Here's some progress shots on my staircase stripping project back in '01.
I learned how to do this at the feet of a master: my neighbor, Joyce Lariviere. She and her hubby have been fixing up old houses for 30 years and her specialty is paint stripping. She and John did an amazing job on the cherry woodwork in their current house. I've always hated paint stripping but Joyce taught me how to, if not love it, at least make it tolerable by approaching it more methodically than I had in the past.
First is the equipment. You need a heat gun to remove the top layers of paint. Heavy rubber gauntlet gloves (mine are track worker gloves given to me by a subway electrician). An assortment of 1-1/2" to 3" spackling knives, preferably with wooden handles to insulate them from the heat. A few dental picks and an artist knife for the details. Stripper sponges (used for scrubbing the surface after most of the paint is removed). A wire stripper brush. Lots and lots of paper towels (pre-rip these into a pile). A 40-gallon plastic garbage can with bag liners. Lots of rubberized canvas drop clothes, taped down. Fabric booties or old shoes (remove them before leaving the tarped area).
I depart from some of the other advice here by preferring the nasty strippers. I really haven't found any of the "green" strippers to be as effective as stuff like Rock Miracle and KleanStrip, which is what I see the professionals use. Used as directed it won't ruin your woodwork. I've used at least 20 gallons of this stuff in this renovation without any damage and this is all woodwork that was refinished naturally, not repainted.
Use the heat gun to remove as much of the paint as you can. Heat up an area enough to get a knife under the paint. Then slowly move the gun, trailing it with the knife. Don't overheat the paint. If the paint starts to blister, move more quickly or turn down the heat.
Don't try to remove every last piece of paint with the heat gun. 80-90% is good. Also, if the piece was varnished it's going to be difficult to get it all off anyway because the varnish will just liquify under heat.
Switch to the stripper. Lay down a heavy coat with a natural bristle brush. Try to get it on in one swipe and don't back brush. The way chemical strippers work is that they create a top seal almost immediately on exposure to air to keep the active chemicals from evaporating. Back brushing removes that seal.
Work areas no larger than a couple of square feet at a time. Let the stripper work for 15-20 minutes. Then scrape it off. I use a 2" scraper in one hand and hold an old 12" metal drywall knife in the other. I dump the spooge scraped up with the 2" knife on to the 12" knife. When the latter is full, I scrape it off into the trash can.
Re-apply more stripper to the area. Wait about 10 minutes. Then use the wire stripping brush to get into the grain and details. Wipe down with paper towels.
Re-apply more stripper. Wait about 5 minutes and attack the details with the picks and artist knife. Keep the points clean with a wad of paper towels in the other hand.
Completely work a small area at a time before the residual paint has a chance to harden again. It will make the job go more quickly.
After you've finished, wipe down the area with a product called After Wash, which is basically MEK. It's nastier smelling than the stripper but it does a great job of neutralizing the chemicals and removing any film.
Wait 24 hours. Then sand through the grits. If it's a piece of furniture, you might also want to apply a sanding sealer to raise the grain before sanding. Needless to say, wear a dust mask for sanding.