If you bag your grass when you mow, thatching won't be an issue for at least a few years. I generally rake my lawn thoroughly each spring (as soon as I can get to it, so spring rains can penetrate well) and fall. And yes, 4 or 5 shots of fertilizer each season will really establish good solid, thick roots so your grass will survive from year to year.
The worst thing I have going in my yard is clover - both Dutch (white flowers) and sweet (yellow flowers) varieties. 2-4-D will kill it, but it will kill almost everything else, as well. I try to stay away from chemicals for weeds, but sometimes.......
Aerating is likely every three to four years, depending. If you hire a company to take care of your lawn (I used to) they should be able to tell you if it needs to be done or not. They may also tell you it needs to be done even if it doesn't, hopefully you can find someone you know and/or trust.