This was my first ever PETG print and I had a hard time with it at first. If you're having issues getting it to stick and you're using a smooth build plate like from Prusa do this - wash it with dish soap and water, let it dry really well. Then go over it with Windex or any glass cleaner I suppose.
Lastly, I used "Warkocki's Pretty PETG" Slic3r profile and it was like magic. It takes 2x as long as the default Prusa PETG profile, but it is much, much better.