I usually just spin them in my arrow straightener to check them. You can make your own (spin checker) out of just about anything. You can use a cardboard box and a soda can. Just cut out a "V" exactly the same depth in each end of the box , the box should be big enough so your fletchings hang off one end and your broadhead out the other end. Then you can use anything you want such as a soda can or whatever , just elevate it so it's at the same height as your broadhead. Put a small dot on the soda can , place the soda can so the tip of your broadhead is touching the dot , slowly spin the arrow while watching the tip of your broadhead on the dot. If it's good the point of your broadhead will stay inside the dot.

I hope you can make heads or tails of what I tried to explain. When you get to know what your looking for you can just spin them in your hand to check for straightness also , but for liability reasons I'm not going to try and explain that one.

I bet if you did a search on the net you could find a site that explains how to make a homemade spin checker alot better than I explained it.