1. ABS vs PLA
ABS stinks to print with, but probably not enough to be detrimental. PLA kind of smells like popcorn, which is awesome. ABS is stronger because its a little flexible and can take higher heat. PLA is more stiff and shrinks less, giving more accuracy, less warping, and a faster print. PLA is biodegradable, as it is made from corn starch.
2. It's a hobby
Expect to be fine tuning and diddling for hours. Not because it's broken, but because you want perfection god dammit. Nothing worth doing is easy, and practice makes perfect. Fine tuning your machine is almost as much fun as printing.
3. It's slow
-You're not going to have a fast print. Our current technology doesn't allow for that...yet. Patience is a virtue, and it will serve you well not to rush. Trust me though, the wait is worth your awesome new print.
-Seriously. If you want a cheap, good quality 3D printer, it is the way to go. There I just did the research for you, you're welcome. It's about a 20 hour self build but the directions are outstandingly detailed, and it comes with pictures and a bit of humor!
5. Don't crowd fund.
-Do not crowd fund a 3D printer. It's stupid to pay for beta testing. You want a 3D printer that has been thoroughly tested. It will save you time, money and heartache.
"It's a trap" -The Admiral
6. Be creative!
-You can mod your printer to laser engrave/cut. 3d print in PLA make a mold from it, and then melt away the filament. This gives you a great platform for metal casting. The possibilities are endless.
7. Resin VS Extruder
-If you want resolution get a resin 3D printer or look into using acetone with ABS as a smoothing technique, when using an extruder. Extruder 3D printing tends to be cheaper due to it's mechanically simpler setup. Resin 3D prints are excellent for exact sizing, this would be good for professional modeling and figurines.
-You can leave a print running all night and wake up to a sad, sad pile of spaghetti. Stop crying, you can make it work. The printer can't support things in mid-air. For example, if you draw a letter "C" from the bottom up, you get to a point at the top right of the letter where part of is expected to float in mid air. Either lay it down when printing or use a "scaffolding" option in your Slicer.
9. List ideas
-Write a big list of every thing you want to print while you're waiting for the printer. All those times you've said "oh man, if i had a 3D printer..." You'll really appreciate it later.
10. It can pay for itself.
-If you have a car with a missing connector? Replace it! Need a new cellphone holder? Make it! Need a project box? Craft it! At least this is what I told my girlfriend when I dropped 1K on a 3D printer.