Backflips are easy, the 1st one's always scary though. If you balls up and do it, I guarantee you'll land it within 5 tries. One of the easiest tricks to do once mastered.
Frontflips are harder, not because of the rotation, but because your blind for most of the trick. You'll get it if you give it enough tries, remember to pop off your jump so you don't go headfirst into your own lip.
Lincoln loops are tougher, because like posted above, you usually end up spinning and dying. Practice them on trampolines first so you can know how to throw it, and what it feels like. Same thing as on a tramp, just slower rotation, and with more weight on your feet.