I hate matching an existing finish that is stained. I'm not very experienced with it, and don't have tons of money to spend on fancy dyes. So I end up spending a lot of (elapsed) time trying different variations, using the few different kinds of finishes I own. I'll occasionally buy a small can of stain to add to my collection, but I do so little staining it's not uncommon for it to get too old before I use it up.
I've been reading Bob Flexnor's "Understanding Wood Finishing" and Jeff Jewitt's "Complete Illustrated Guide to Finishing". Both are excellent books, but I'm such a newbie that it's just barely better than trial and error. I think part of the issue is that my eye isn't very well trained. As a result, I don't see the subtle shades of red or orange or whatever until I hold my sample next to the piece I'm matching.
I need to match a finish because I'm making a small display cabinet (a sort of shadow box) for my mother-in-law, and she wants me to match the stain on the cabinets that are near where the display case will be installed. Unfortunately, the existing stain has some subtle shades of red and orange to it that are proving hard to reproduce. I think I may be narrowing in on an answer, but I won't know for another few days, as it will require a few more experiments with stain and shellac to hopefully achieve a look that is close enough to mesh with the existing cabinets.
I can't decide if I want to get enough staining experience to make it easier, or if I want to just forget about staining and pick my wood species to be the color I want.
Of course, neither option matters right now. What matters right now is finding a color match so I can get this long-overdue piece finished and installed.