I've been reloading for less than a year, but it helps me to think of powders basically having three characteristics I care about: burn rate (which influences how much pressure you get and how quickly), meterability (I use a turret with a thrower, so one that meters well matters to me), and case fill (powders that fill the case are more forgiving, but you'll also get fewer loads per cannister, generally speaking). There are other factors, such as sensitivity to temperature and cleanliness of burn/soot, but the first 3 are the ones that I focus on.
Find a manual with a burn rate list - I think Hornady has one. Get a feel for which powders are fast, medium, and slow (relative to rifle or handgun). Look at the load data for a caliber (and bullet weight and type) you're considering loading... is most of the data for fast, medium, or slow powder? OK, now go back to the powder rate list. The powders in that general area on the list may be suitable. You'll still need to find load data, though, since the density/fill will be very different - NO SUBSTITUTIONS (with the exception of a couple of powders specifically designed to be substitutable). But by knowing that you need a fast powder, or a slow one, and having a general sense of what are fast powders, you can keep an eye out for them.
Is that all too hard? Well, when you find a powder available, go to the powder maker's website - almost all of them have some online data available. Pull the data and see if your caliber/bullets are listed!
