Leaves, to bag or not to bag.  Leaves can be a culprit or a benefit, depending on how you treat them.  Too many leaves left to lie will block sunlight, promote disease and cause problems for the lawn.  Leaves mulched to fine pieces will provide valuable nutrients (organic matter) for the soil.  However, too many mulched leaves have the same affect as leaves left to lie on the ground.  Begin mulching (by mowing) leaves just as they start to fall to the ground.  When the "big" fall comes and a large piling of leaves appears on the ground, remove these leaves from the lawn.  Then return to the practice of mulching the leaves as part of mowing.  The rule of thumb, do not let leaves lie.