I live in Washington State and I am wondering what steps I should take to winterize my lawn. Both my back yard and front yards get about half a day of sun each day. There are some spots where moss is starting to take over and some spots that are patchy and dead. I bought the house in May and at that time the lawn had been airrated (spelling?). I think that now is the time to add grass seed and fertilizers, but do I need to prepare the lawn first? The parts of our lawn that are bare have compacted dirt so how do I prepare that for seed? Help is greatly appreciated!

Apply horiculture lime to areas of moss to kill it off.

Culivate compacted soil with a roto tiller available from any rental store.
Adds some peat to areas you are tilling to improve soil areation
Apply your seed now and cover with topsoil or peat water thourghly and then water everyday.

Adding some rye in your grass seed mix will help to shelter new grass and encorage birds to eat rye instead of grass seed. Rye is an anuall grass and will die off next summer it will overwinter giving a green lawn and prevent soil from washing away
Apply scotts winterizer fertilizer to improve winter hardyness.
Next spring apply scotts fertilizer for a quick green up and nice lawn