Its hard to see how big the slope is but I would rake the snot out of it with a metal rake, aerate it, add some top soil where needed and top seed it. If need be put biodegradable mesh over the sloped area to avoid wash away.
When you say add top soil, how do I do that? Do I just toss it on, make a college effort to spread it around sort of evenly across the lawn, and call it good? Or do I need to do something fancy like compact it so it stays in place? Take care not to cover up the grass so much that it is smothered?
I'm going to go for a soil analysis as recommended here, but from my initial look I may need more top soil (there are a lot of rocks in the dirt, and that combined with the crappier grass quality might mean the soil quality is poor). I might need to get a ton of top soil...
Yea for sure go to a a good lawn care supplier and take close up photos as well as bring samples in and tell them how you feel about chemicals etc.. There are always alternatives but like alot of things some work better than others and some can get pricey. As far as the topsoil goes usually first you need to determine how much you need and then if you need enough its cheaper if you just need a yard or two then its cheaper to pick it up. If you have a Riding lawnmower and a trailer that would be easiest to shovel out of other wise wheel barrow and make piles as far or as close as you need to. They make a topsoil spreading rake that would be worth renting for a day and its just a much bigger metal rake but basically just rake and spread evenly over the whole area. Any lumps bust up but you want screened topsoil. If you spread and rake it will lay out just the way it should be. Top seed it and and depending on grade use the biodegradable screening I was talking about or lay down straw otherwise it will wash away and birds will eat a ton of it. But aerate first and seed before you add more topsoil and seed over the top of that as well. You will get a good deep root system and based on your picture it wont take you a half a day to do it. Couple hours tops.
For those that asked, yes, the front lawn is sloped. The house is on top of a hill, so the slope is gradual at first and then becomes more steep. Towards the bottom it is fairly steep, but not so steep that I wouldn't be able to mow it with a regular lawn mower... I don't know the grade off the top of my head.
I checked the lawn yesterday; there is at least 6 inches of topsoil there. Small rocks (~1 in) are loosely mixed in throughout the lawn, which I am guessing is a result of when they dug it up for the leech field, and did a shitty job of putting it back together. Anyways, hopefully it's good enough to get me going.
Anyways, my plan is toe aerate, maybe de-thatch, seed, cover with some hay or something like that, and water for a couple of weeks. Water on any sort of permanent ongoing basis will probably never happen. Very fortunately, sprinkler systems do not seem to be part of the culture of the area I live in; surprising, since I'm sort of in a fancy pants area... but I am east coast now. Previously I lived in conservative mid-Michigan, where EVERYONE had a sprinkler system. The area was humid with flooding a common major problem, and it was common to see sprinkler systems on while it was raining. A great example of some of America's cultural problems.
I checked out the microclover that was recommended. It seems like a good concept that meshes well with me personally, but I am more doing this for my wife as well as keeping up property value. I am a little nervous that common preference is to see actual grass; people tend to think of clover as a weed, sadly. Therefore, I may also look into grass that is an optimized mix of looking 'regular" (plush, green, 'healthy') and is good for the lazy homeowner.
I live in the PA/DE border, so climate is standard mid-Atlantic region. Mild-ish winters with occasional big snows, brief spring/fall, and hot/humid summers. This past year had record breaking rain fall. I suspect future weather will bounce back and forth between wetter years and drier years. A flexible/resiliant grass is preferred, but by no means is our climate as dry as California/southwest regions; there will be rain. Also, the front lawn gets full sun... so I'll have to get a grass that thrives under those conditions.