The above advice is great and here is another option that I'm forced to use. Sometimes we get a lot of rain here and it prevents me from mowing at the best time so the grass grows really fast while the sun is shining drying out the yard to a point that I will not get stuck in the mud and when I do finally get to cut the grass there are big clumps of grass that pile up and look ugly. Several things I do to help prevent this: Keep the blade(s) sharp, set deck to middle of height range and when finished mowing, raise deck height to maximum and and drive over the clumps with the blade(s) spinning as this will help further cut up the clippings and disperse them over a larger area. I know this means going over the same spot two or three times but it does work well for me.
I wish I could cut the grass more often but more times than not, rain prevents me from doing so. What kind of grass do you have that grows better in the shade under a tree?