Purchase some cheap, already slabbed nickels. Until you actually hold a graded nickel in your hand and look at it under magnification, you'll be better able to grade your own coins. I see people dumping their lower graded coins for way less than the cost of grading and wondered why. Now that I have bombed on several of my submittals to PCGS, I was about to dump several of my own duds on eBay for cheap just to rid myself of these useless planchets... However, then I discovered its nice to have several grade levels for personal reference and I do look at them often.
I found that those printed photo grading guides will get you close but once you start talking about MS65 and up, you really need to see it up close to appreciate what makes up those higher grades. Also, PCGS has some decent videos on what goes into grading which includes more than just wear, scuffs, or misc marks so check out their grading videos.