When rolling out sugar cookie dough, how do you get it perfectly flat? I'm new to sugar cookie making and they are always lopsided 

Go to the hardware store and get a couple of 2 or 3 foot pieces of wooden lathe in the lumber section.  It is a little over an inch wide and a quarter of an inch thick.  Very inexpensive.

Place them about a foot apart on your counter so your rolling pin can rest on both of them with some of your cookie dough between the sticks.  Roll your dough out.

Your cookies will have a perfectly even thickness.  If you want thicker cookies, get thicker sticks.

I second that. I bought my pieces of wood at Michael's. It works like a charm.

I agree with the above - I have balsa wood square dowels that I got from Michaels in varying thicknesses.  What I use most often are the sizing rings that are widely available.  They slip on either end of a rolling pin and come in various thicknesses.  I very lightly flour my big silpat mat and roll out the dough with plastic wrap on top.  lift and release it frequently so the dough spreads out nicely, and lift the whole thing and rotate now and then so it doesn't stick underneath.  the plastic wrap makes a very smooth top, and the cookies are uniform thickness.  The plastic also means less flour, so the re rolled scraps are not altered as much.  HTH

At first I was using the 2-piece wood idea and that worked ok, but the wood would shift on me and it got annoying. I make a lot of cookies so I bought the Joseph Joseph Adjustable Rolling Pin Plus that has the removeable pins on the sides and I love it. They sell it on Amazon, but I had a $10 off coupon at SurLaTable so I got it there. If you are thinking about this rolling pin, just be sure to read the feedback on Amazon. It says the pin is 16.5 inches but the actual pin is 13 inches. If you include counting the pin area, then it's 16.5. Just so you are aware.

www.amazon.com/Joseph-Adjustable-Rolling-16-5-Inch-Multi-Color/dp/B0091QO3RK/ref=cm_cr_pr_product_top

You have to decide for yourself what works best for you. You may not want another rolling pin to deal with. I originally started using chop sticks or wood pieces, but because I make a lot of cookies, I now prefer this rolling pin. Just my preference.

Awesome! Thank you all so much! I thought about using wooden sticks because I would use that method when rolling out clay but I wasn't sure if it would work with cookie dough. I do plan on making a lot of cookies so I might check out that rolling pin. Thanks again :)

I make a ton of cookies too and I never have problems with the wood but I roll on a non-stick mat I bought at Sur La Table so maybe that helps them not slide on me.

The wood sticks should give you the uniform cookie thickness you're wanting. I splurged and bought a DoBoard a number of years ago, and love it. Yes, it was expensive, but well worth the cost for me. Check into it if you aren't happy with the MUCH cheaper wood sticks. (I also tried the rolling pin rings, but didn't get the uniformity I was after).