I use the following procedure and am able to print multiple parts without leveling in between each print. I don't use anything to make parts stick and rarely have any issues. I'm running repetier firmware 0.92.
1. Level the bed somehow enough to get http://www.thingiverse.com/thing:526058 these new adjusters printed. They will make a massive difference in the ability to quickly adjust the bed.
2. Unload any filament
3. Move the bed down and clean it really well with water. Remove whatever tape, hairspray, junk, glue, etc so you only have nice clean glass. Use water and then isopropyl alcohol as your last two steps. Clean the extruder really well too. Use a small wire brush like the one that came with the unit. First clean it cold, which won't do much, then heated. I print at about 215, so I clean mine at that temp.
4. If you haven't already installed the new adjusters, do so.
5. Get a feeler gauge, probably from an auto store or Sears or similar. You want a gauge that has a 0.100mm shim. Mine is a 0.102mm, so don't drive yourself crazy trying to find a perfect one, just get as close as you can and know for sure what it is.
6. Now, everything should be clean and ready to start.
7. Heat the bed to the temp you will print at. I use 105c. Once it gets there WAIT for 3 to 5 minutes. This lets the whole bed equalize in temp, which is how you should print too.
8. Now heat the extruder to your printing temp. I use 215c. You don't have to wait on this one.
9. Be sure the head is homed.
10. Move the bed down to 5mm with gcode: G1 Z5
11. Now move the head to the front of the bed: G1 X100 Y180
12. Now you are going to carefully lower the bed to roughly adjust the front. Use the move command to lower the bed mm at a time. When you get close to the bed, adjust it so the head never touches. After you get to 1mm, lower the bed by 0.1 increments until you are at 0.5.
13. Now raise the bed to 5mm and then move to the back left corner (190, 30). Lower the bed again the way you previously did.
14. Raise and move to the back right (10, 30) and lower again.
15. Now the bed is in the ball park and its time to do a final adjust with the feeler gauge.
16. Start at the back left and this time move the bed to the same height as the gauge size you have. I feel its best to make the gauge not fit and then slowly increase the gap with the adjuster until the gauge slides freely between the nozzle and the bed. Your technique may differ, just be consistent.
17. Raise the bed, move to the back right and repeat. Now do the front of the bed.
18. If paranoid or anal, go recheck them.
You're done! Using slic3r, I can print on the glass with nothing else. Every 3 or 4 prints I clean the bed warm with alcohol. The only time I have messed with releveling is if I change print temperatures.
The above really only takes about 5 minutes or so, most of which is waiting for the bed to heat.
