Right now? Not much. March and April are lazy months on the lawn.

When the forsythia blossoms (6a is a wide zone, so a locale is helpful), putting down a pre-emergent like Dimension 0-0-7 or Stonewall 0-0-7 will really help reduce your weed problems through part of the season--three to six months respectively depending on which product you use. For you, that's likely to be April sometime.

Feed the lawn with any good lawn fertilizer (not a Weed and Feed) around Memorial Day. It seems late, but that's when lawns want to eat. Choose anything with a high first number, and low second and third number (like 35-0-2, or 32-2-6, or something like that). Just get the cheapest, they're all about the same, and choose something with very little slow release nitrogen--it's cheaper and you don't need it.

Feed again on Labor Day, October 1st, and (optionally), when the lawn stops growing and you do the last cut for the year. That last one helps store food for the following spring and healthy growth and really helps, but you can skip it if you want.

Spray weeds with any good spot-spray, like Ortho Weed B Gon--I go with the Clover, Chickweed, and Oxalis as having a very wide-spectrum kill and taking out most weeds. With the pre-emergent, weeds should be down about 90%, but you'll still get some.

If you water the lawn, do it infrequently and deeply. 1" at a time would normally be optimal, but it does vary (a tuna can is 1" deep, which will help you measure). Once a week would be the normal minimum. Very hot weather can mean irrigating more often, but less.