1) 99% of any thing from about 1988 to 1995 or a little later is junk - that's where manufacturer's decided there was lots of money in cards, so they upped their production and devalued everything.

2) I just ran across Collx recently -is seems like a good software - use the app scanner on your cards and it will tell you what they are selling for. I also check Ebay prices - go to the Sold values only - people can list things for anything they want, but actual sales are what is important.

3) Graded, autographed, or numbered (like #1/10 or #2/5) sell better - graded is the best seller now (it costs a fortune - and most of the graded cards sell for less than the cost of grading - but when you grade a bunch of them, you'll get some winners that make it all worth it.

4) Ebay, Collx, and Facebook Marketplace are all places you can sell.

5) Pretty much the only thing I collect now are signed BYU or LDS Player cards and Memorabilia

6) I have a bunch of 50's and early 60's cards I need to work up the ambition to sell, but I also have about 70,000 cards that are all stars or minor stars, and are basically only useful to donate to DI or Salvation Army and take off my taxes (that's where all my commons went)