Growing a good healthy lawn starts with making the soil that lawn is growing in into a good healthy soil. What is the level of organic matter in your soil?
What is your soils pH?
How well does that soil drain"
How well does that soil retain moisture?
How is your soils tilth (workability)?
What kind of life is in that soil?
What is the nutrient balance of the soil?
Contact your counties office of Purdue Cooperative Extension Service for information about where to have a good, reliable soil test done and then dig in with these simple soil tests,
1) Soil test for organic matter. From that soil sample put enough of the rest to make a 4 inch level in a clear 1 quart jar, with a tight fitting lid. Fill that jar with water and replace the lid, tightly. Shake the jar vigorously and then let it stand for 24 hours. Your soil will settle out according to soil particle size and weight. For example, a good loam will have about 1-3/4 inch (about 45%) of sand on the bottom. about 1 inch (about 25%) of silt next, about 1 inch (25%) of clay above that, and about 1/4 inch (about 5%) of organic matter on the top.

2) Drainage. Dig a hole 1 foot square and 1 foot deep and fill that with water. After that water drains away refill the hole with more water and time how long it takes that to drain away. Anything less than 2 hours and your soil drains� too quickly and needs more organic matter to slow that drainage down. Anything over 6 hours and the soil drains too slowly and needs lots of organic matter to speed it up.

3) Tilth. Take a handful of your slightly damp soil and squeeze it tightly. When the pressure is released the soil should hold together in that clump, but when poked with a finger that clump should fall apart.

4) Smell. What does your soil smell like? A pleasant, rich earthy odor? Putrid, offensive, repugnant odor? The more organic matter in your soil the more active the soil bacteria will be and the nicer your soil will smell.

5) Life. How many earthworms per shovel full were there? 5 or more indicates a pretty healthy soil. Fewer than 5, according to the Natural Resources Conservation Service, indicates a soil that is not healthy.
to see what you have now and determine what you need to do to make that soil into the good healthy soil.

Hi welcome to the forum.

There are a few basics to lawn care. If you follow them you will have minimal weeds. Apparently your predecessor was not following them. And they are not necessarily a natural thing to do so you might not be following them, either. Here they are.

2. Water deeply and infrequently. Deeply means at least an hour in every zone, all at once. Infrequently means monthly during the cool months and no more than weekly during the hottest part of summer. If your grass looks dry before the month/week is up, water longer next time. Deep watering grows deep, drought resistant roots. Infrequent watering allows the top layer of soil to dry completely which kills off many shallow rooted weeds.

3. Mulch mow at the highest setting on your mower. Most grasses are the most dense when mowed tall. Bermuda, centipede, and bent grasses are the most dense when mowed at the lowest setting on your mower. Dense grass shades out weeds and uses less water when tall. Dense grass feeds the deep roots you're developing in 1 above.

4. Fertilize regularly. I fertilize 4 times per year using organic fertilizer. Which fertilizer you use is much less important than numbers 1 and 2 above.
   

You cannot overseed in May and get anything but more weeds. If you want it green, then suffer through this season with the weeds. Water, feed, and mow them and they look pretty good. Then in the fall you can kill the crabgrass and overseed.

Dandelions can be plucked out with a Weed Hound tool or you can spray the individual weeds with Weed-B-Gone.

I spot spray at times too...Sometimes you have to do what you have to do.

I feel it is a lot better than blasting the whole lawn w/ chemicals, which 90% of the population does as they put down Scotts, lesco, etc.

Oops! Sorry for that. I have been over on the regular lawn forum for so long, I forgot where I was.

The Weed Hound tool is excellent. It's available at Home Depot.

I had very good results with CGM this year. I was battling crab grass last year but this year zero problems.

Some weeds are good as you transition to a healthy lawn. They tell you the condition of the soil, I let most dandelions go but I don't let any weed reseed. Most any weed can be removed fairly easy by hand if you follow San Antonio's flood, famine watering techniques. I tought him that. Yuk, yuk yuk.

Take your soil samples and send your local Nursery to test them. After that use corn gluten meal for pre-emergent weeds. Remove weeds by hand or digging. Reseed entire lawn to remove the patches. Keep your lawn mowing during summer months.

I have yet to find a nursery that tests soil samples. Many of the state universities Ag Schools will through your state universities Cooperative Extension Service, however.

Search Nearest in your area you will get it or your can search online also.