well you better start now before it gets hot

If you want to do it on the cheap then
buy a dethatcher attachment for your lawn mower
run it a couple times if you have a tractor run it
more then a couple times

then spread weed and feed this will kill your weeds

get a 5 gallon pump sprayer and spot spray big weeds

let the lawn sit about 10 days and dethatch again
then

goto servicestar / agway and get a couple big bags of seed

cover the entire yard and dont walk on it much just keep it wet
for about 2 weeks


then in about july you want to weed and feed again but very lightly
then in the fall put down lime

every year you will have to spread Weed and feed fertalizer to kill the
weeds and promote grass growth

also watering

if you water just a little that will make the weeds grow and the grass
wont get enough water to grow

You wont believe how much you have to water to get the soil moist
down to 2-3 inches It may take 4 hours overnight but it is a lot of water

so its best to buy grass that can grow in direct sunlight in hot climates
and then dont cut it too often because that will require more water
and the stalks of the grass as they grow high will shade the roots
of the grass keeping them cool and in need of less water


other then that you can hire someone and expect to pay a couple thousand
depending on what they want to do. but in the end next fall you wont have a
better lawn even if you resod.