If you are going to rent an aerator, you may as well aerate and seed the whole thing at once. Seed is fairly cheap. The sooner you get a decent strand of grass growing, the easier everything else becomes.

As for topsoil, if you have low spots to fill, go for it. If you are just looking to improve the soil, you are better of topdressing with compost. That isn't something you have to do all at once though and you only need to apply 1/4" to get a big benefit.

Are you looking for a showcase lawn or just a nice lawn for the kids to play in? If you are going for "the nicest lawn on the block" just roundup everything first. If you want "nice" you can leave the existing grass. Either way, you want to wait until the temps are 80 or so. Mow the existing lawn short and rake up the clippings. Rent an aerator and make several passes in crossing directions. Fill in any low spots with topsoil. Spread seed and fertilizer. If you want to topdress with compost, do that next. Then you just have to keep it watered - 2 or 3 times a day is best - until it comes up.

If you are going for "the nicest lawn on the block" just roundup everything first.

billl? Is that you or an imposter using your name??? Have I ever seen you suggest using roundup before?

Other than disagreeing with that (I'm never in that big a hurry), I would add that you can rake the aerator plugs from the high points of your hard to the low spots to help fill in low spots.

When I was in Memphis, most of the lawns I saw looked like warm season grasses. If you're going to plant a warm season grass, I think you want to wait until late spring to plant.

Thanks for the help!