Question
my lawn is only 3 yrs old (new home) and i am having problems with bare spots/ thin spots in my lawn my soil is very rocky...how do i fix all the bare spots? it's about 60% of my lawn

Answer
Hi Chris, Bare spots can be caused by a number of reasons.  Soil compaction, root competition from trees, fungal disease, insect damage, improper pH and soil fertility, improper grass type.
First make sure you are growing the right grass.  Is it full sun, part sun, mostly shade?  Your local garden center can help you decide which grass type is best for you.  
All turfgrass likes about the same pH, so check your pH and adjust it to 6.5 if you need to.  I'd aerate the spots and then seed or sod again.  If you think it might be fungal, treat the yard with a fungicide before you plant.  You local garden center should have a lawn care program printed for you to follow.  Jim