I have just classified my 700th star on Planet Hunters. It took a little over a month to reach this number. I think practice and patience have been the two most important things that made me feel a lot more confident now when I mark transit that I was when I started contributing. Dips aren't always clean and smooth like the ones in the tutorials or in some of the examples. Most of them are very subtle, especially when you're dealing with Earth-sized planets or with Giants with irregular pulsations.
Classify, classify and then classify again! That's how you'll get used to it, that's how you'll learn. It's a bit frustrating at the beginning and you may make a lot of mistakes, like marking an eclipsing binary or a pulsation. But practice is everything.
I compiled a list of useful links for planet hunting:
Examples of quiet stars
Examples of variable stars
Examples of pulsators
Eclipsing binaries
Kianjin's planetary calculator
Transit shapes
Identifying transits in Irregular Pulsating Giants
Explanation of transits
Examples of transits
Huge collection of transits
