Agree with Jacquie ... square em up!
I also attach a post it note to a block if I find that it is a tad short (less than 1/4") - I'll put a post it on the side that should be "compensated". That way when it comes time to put the blocks together I know that this one is going to be shy of the intended size and I can compensate for it when I join them together. I can't leave these things to memory!!