Man, what a broad subject. Are you talking stains, top coats, a combination of both? Polyurethane or varnish or BLO?
Most of my projects these days are functional furniture and cabinets. I use a variety of oil stains on most woods but have begun relying more on dyes to get a deeper luster to the wood. Since everything has to be functional, I have gone to Valspar conversion varnish applied with an air assisted airless. The CV has good UV protection, is non-yellowing, and almost impervious to common household chemicals.
Artisan Woodworks of Texas- www.awwtx.com