You can also use a small loupe to inspect it. A lot of swiss army knives come with a magnifying glass you can use, as well. Of course, magnification doesn't do all the work for you, ya need experience. I still have trouble figuring out what is what, there are so many kinds of leather, and a lot of things that are 'real leather' still aren't desirable to me.
However, if you keep that loupe on you, and inspect different kinds of leather, you start to be able to tell them apart. A burnished genuine leather doesn't have the same sort of pores as real grain, etc.
What's really bad, is when you're trying to buy something online and they just label it "leather" without any super high def images to look at. Myhabit.com is especially bad about this, imo.