Scans are worth three points if you add the front, and then back of the same card. Adding only the back is 1 point, and I believe adding only the front is 2 points.
Adding a checklist is 5 points, and adding an External Link to a player, team, or set page is 1 point.
Other edits, such as teams, names, notes, and the like are also awarded at the end of the month. There is no known point value for these activities. I assume Admin has some algorithm behind the scenes to do the calculation.
Activites such as posting in the forum, conducting transactions, or anything else that does not constitute "editing" the Database itself does not award any points, nor are they randomly awarded for milestones or anniversaries (I know that SportsCardForum does 100 SCF Points for your birthday - that isn't the case here).
The idea is that earning points for site edits shows an understanding for how the site works and functions, and that is why points are 1) used for determining the higher permission levels (which come with the most Database editing power) and 2) not awarded for site activites that do not have any direct influence on the content of the Database.
I'll never quit collecting entirely, but I am downsizing. Check out my COMC store and help me thin out what I don't want so I can buy cards that I do want. See something you like? Send me a message on here, and we can knock the price down quite a bit. I'll even take a bit of a loss if it means getting you a card you really want.