This is what I did: I used weed and feed about 4 weeks ago, and it killed some of the clovers, so I just did it again today (on the areas that still had healthy weeds). What should I do to grow new grass in place of the large dead areas? It looks worse than it did in the beginning actually! I thought the "feed" in weed and feed meant that it feeds the lawn as well...but it just looks like everything is dying.

I appreciate any help on this!

You'll need to tell everyone where you live so that they can determine what type of grass you have. If you have a bunch grass variety then it will not spread and you'll need to overseed it. If you have rhizomatous grasses, then it will fill in but will take some time.

If you have any unopened bags of weed and feed, return them and get your money back. Tell them you want to exchange them for fertilizer and herbicide. You are about the millionth person to write her with similar results. They sound great but they just don't perform. The reason seems to be that weeds in good health die better than weak weeds. If you fertilize now, then come back in 2 weeks and spot spray the weeds with a product like Weed-B-Gone. Since you have clover, get the one that has the word clover in bold print in the name. Like WBG for Clover, Chickeweed and Oxalis.

The puff ball weed is dandelion. That will start you on your week knowledge journey.

You probably need the basics of Lawn Care 101. Here it is.

1. 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.
   


2. 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.
   


3. 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.
   

I appreciate your help. ;)

St Louis, huh. Seems like a lot of people writing in from around there this spring. Thanks for that. Your location is more important than your USDA zone. The zones are used only to estimate how cold it gets. It says nothing about your soil. If you lived in the California high desert or in Central Florida, soil makes a big difference. You have fairly normal soil if there is such a thing.