When I make my sugar cookies, I end up with the top of my cookie having a lumpy finish instead of a smooth finish. I use fondant a lot and because of the lumps, the cookies end up looking like there's random humps. I hope this makes sense. Can someone help please?

when that happens to me, this is what I do...

when I take them out of the oven, I quickly use a flat spatula to gently flatten the tops. It takes 2-3 gentle circles over the top of the cookie, and there are no more lumps.

Not sure if your lumps are like my lumps...
I've had a problem before where the cookie comes out looking kind of like really dry skin! Almost like you can see big skin cells! I know this probably sounds weird, but if you're having the same problem I am, you'll know exactly what I mean! LOL!! I'm in the process of trying to figure this out, but it seems to look better if I mix the dough a little more thoroughly. Fine line, though...you don't want to mix it so much that you toughen the dough. Good news is that once the cookie is covered with icing/glace, you can't see "my" lumps.

If I have these lumps or bubbles,I do the same thing bonniebakes does and flatten them as soon as they come out of the oven. However, I usually don't have them.

I cream my butter and sugar really well, add the flavoring and the eggs. Then I add about 2/3 of the flour in big spoonfuls, keeping the mixing speed as low as possible. I mix the rest of the flour in by hand.

I also roll the dough out as gently as I can. so in other words be kind to your cookie dough I think it helps keep the lumps and bubbles away. JMHO

Thank you everyone for your help. Linedancer, I'll give your technique a try this weekend.

Linedancer said that same thing I was going to. You do not want to overmix and thus adding too much air to your dough which will give you those air pocket bubbles.