Oops, sorry! I missed this (itch didn't notify me about a reply)
For Dan's bad ending, it's easier if you play on normal (rather than easy) mode. Tell Janet at the beginning that you *don't* like threesomes, and generally be clingy and pressure him to be monogamous once you're dating
Campus Map Piece 1 is obtained on October 8; you have to be dating Carlos, you have to have explored campus on August 26, and you have to go running with him in the morning
Golden Pendant is when you are going down James route but he doesn't like you enough to start dating... put the game on normal mode and don't trigger the "special" James scenes (don't explore campus on August 26, don't catch him on IM September 23 when he asks you to go over); you'll get it on October 13
Cross Sticker is obtained October 27 if you're dating Dan and you give him responses that suggest you don't want sex (I guess we could do that, Was thinking more the sex part). You'll watch Bad Education together instead of having sex after dinner
Black Plastic Ring is obtained for breaking up with Dan at the end of the game, so you'll get it once you get the achievement