I'm fairly new to 3d printing, but there's a few things I've learned that others seem to make much more difficult than it needs to be.
The best thing I've found to hold the prints on is 1 part Elmer's glue all, and 2 parts water, paint the glass with it, then slant the glass perpendicular to the direction of your brush strokes so it like of levels itself. I did this, and printed hundreds of prints before I had to 'repaint' the glass. I use a multi-purpose scraper from the hardware store to scrape my prints off, and it really doesn't scratch the glue off. The prints pop off pretty easy by themselves if you decide to wait long enough for the glass to cool.
Next, with this method, you have to make sure you let your bed reach your set temperature (I do mine at 100 for PLA) and let it continue to heat for a while after it reaches your temperature so the glass reaches that temperature too.
I hold the glass on the bed with the blue painters tape on the front and back, that way when I have to peel it off, it doesn't pull the kapton tape off that's wrapped around the sides of the bed.
Next, BED LEVELING. I spent SOOOOO much time trying to level the bed with a peice of paper. "Adjust it till you feel slight tension on the paper".. What's slight tension? That's a very non-universal term. And if you get a little bend in the paper, even an unnoticable one, it throws everything off. If it works for you, great, I've never had much luck with it, and it seemed like I was constantly trying to adjust the level.
I use a different method, and the only times I've had to relevel my bed were when I changed from kapton, to a peice of glass, to glass with tape on it. I don't think I had to relevel when I switched to the glue.
So, here's my method: I made a hollow rectangle about the size of my print bed, basically a picture frame, maybe a 1/4 inch (6-7mm?) wide, thickness of the rectangle doesn't matter. Next, position your printbed so there's an obvious gap between the print head and the bed. Now, start your print. As soon as your printer starts to print the rectangle, raise the bed until the filament sticks. let it print around, adjusting the other screws too so it's sticking to the bed. cancel the print, clean the bed, and print it again. if it doesn't stick from the start, raise it a little more and restart it. Once it sticks from the start, let it print, when it finishes, measure the height of each side to assure they're all pretty close to the same.
A third issue I've had is the first level would SOMETIMES print very very very thin or not at all, sometimes clogging the printhead, sometimes it starts printing on the second level(Maybe you're bed's not level!? Nope, not the issue.) I found I was actually printing TOO HOT. I never figured too hot would cause that, but I dropped my temperature 5 degrees (PLA at 210) and it now successfully prints the first layer, and all layers after without clogging the printhead or failing to print.
Fourth, when the print head DOES get clogged, (depending on the reason it got clogged I guess could affect whether this works or not) I found 2 different methods that one or the other seems to solve my issue every time.
1) I hit load filament, run it for a few seconds (it's clogged, obviously nothing comes out), then hit unload, and pull lightly on the filament as it's unloading, generally my filament doesn't come out, it'll only come up a little bit. Then after a few seconds, I hit load, and lightly push the filament in until the extruder starts pulling it itself, then in a couple seconds, it starts flowing again.
2) I raise the temperature to 235, then after it's been at that temp for a few minutes, I load for a few seconds, then unload, again, lightly pulling, if it doesn't come out, I load, and slightly push, usually at that point, the filament will drip (like liquid) or pop out the nozzel, then start flowing like normal.
These are just some things that have worked for me, I'm fairly new at this, so, if they help you, great, if not or you've got better methods, great.