Little white flowers? Clover?

Rule of thumb is if your lawn is more than 50% weed, has a weed that is resistant to turf friendly herbicides or undesirable grass interspersed throughout the lawn, kill it all and renovate.

You need to determine what type of grass will grow in your conditions and how much lawn care you are willing to undertake and make a selection of seed from a reputable source.

Unless you have thatch, you do not need to de-thatch. You may have some compaction due to construction so aeration may be useful, try shampoo first and do not till. IN Wisconsin, you'll need to get started very soon if you renovate.

These and other lawn forums are excellent places to read conflicting advice. Lucky you, you have me (ahem! - standing by for the rotten tomatoes). But seriously, I do seem to have a head for collecting best practices and being able to regurgitate them. Neither of the two options seems to consider drainage. You mentioned the yard does not slope away from the house except in one spot. That has to be fixed above all other considerations, because if you start getting water in your basement when it rains, you'll be flipping the house, too. Here's the best tool for getting your drainage right...

Once that's done, put the seed down, roll it with a water fillable roller (rented), and then water the seed to keep it moist, not soggy, for the following 3 weeks. You don't need compost, lime, straw, top dressing, peat moss, herbicides or anything until you get 80% germination on your seed. When you think you have 80% germination (or 3 weeks which ever comes first), quickly reevaluate the coverage. If you have thin areas, reseed right away in those spots. What you're shooting for is a dense coverage of new grass this year before the first frost. Spring is too late to fix it for a couple reasons.

Your soil may not be perfect. Believe it or not I would rather pick up a soil that's had no care for 18 months than one that's been heavily fertilized for 18 months. You can fix it biologically simply by feeding it with organic fertilizer at least once a year and by always mulch mowing the grass. You can fix the soil chemistry by getting a soil test at Logan Labs in Ohio and then posting your results here on this forum (look for where others have posted and see what kind of feedback they get). The $25 test is all you would need.

It's mid July so, as mentioned, you need to get your ducks lined up. As soon as the summer heat breaks, which may be in a couple weeks for you, you can start planting new seed. You could have the soil prep done before that (maybe this month?). Starting early gives the grass time to come in, get evaluated, and a second helping of seed sowed if needed.

In the mean time here's something I wrote a while back on the basics of lawn care. This applies to established lawns, but you can practice it now before you start tearing it up.

Basics of Lawn Care

After reading numerous books and magazines on lawn care, caring for lawns at seven houses in my life, and reading numerous forums where real people write in to discuss their successes and failures, I have decided to side with the real people and dispense with the book and magazine authors. I don't know what star their planet rotates around but it's not mine. With that in mind, here is the collected wisdom of the Internet savvy homeowners and lawn care professionals summarized in a few words. If you follow the advice here you will have conquered at least 50% of all lawn problems. Once you have these three elements mastered, then you can worry about weeds (if you have any), dog spots, and striping your lawn. But if you are not doing these three things, they will be the first three things suggested for you to correct.

1. Watering
Water deeply and infrequently. Deeply means at least an inch in every zone, all at once. Infrequently means monthly during the cool months and no more than weekly during the hottest part of summer. Do not spread this out and water for 10 minutes every day. If your grass looks dry before the month/week is up, water longer next time. If that does not work, then you might have to water more than once per week during the summer's hottest period. 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.

You will have to learn to judge when to water your own lawn. If you live in El Paso your watering will be different than if you live in Vermont. Adjust your watering to your type of grass, temperature, humidity, wind, and soil type. It is worth noting that this technique is used successfully by professionals in Phoenix, so...just sayin.' The other factors make a difference. If you normally water 1 inch per week and you get 1/2 inch of rain, then adjust and water only 1/2 inch that week.

2. Mowing
Every week mulch mow at the highest setting on your mower. Most grasses are the most dense when mowed tall. However, bermuda, centipede, and bent grasses will become the most dense when they are mowed at the lowest setting on your mower. In fact there are special mowers that can mow these grasses down to 1/16 inch. Dense grass shades out weeds, keeps the soil cooler, and uses less water than thin grass. Tall grass can feed the deep roots you developed in #1 above. Tall grass does not grow faster than short grass nor does it look shaggy sooner. Once all your grass is at the same height, tall grass just looks plush.

3. Fertilizing
Fertilize regularly. I fertilize 5 times per year using organic fertilizer. Which fertilizer you use is much less important than numbers 1 and 2 above. Follow the directions on the bag and do not overdo it (unless you use organics in which case you may overdo it without fear of hurting anything).

At this point you do not have to worry about weed and feed products - remember at this point you are just trying to grow grass, not perfect it. Besides once you are doing these three things correctly, your weed problems should go away without herbicide.