By now you should be mowing your lawn. Common Bermuda grass likes to be mowed often (3-7 days) at a height of 1 to 2 inches. St. Augustine requires less mowing (5-7 days) and likes to be cut between 3 and 3 1/2 inches tall.
It is also time to fertilize the grass. At this time I would like to say a word about weed and feeds….DO NOT USE THEM (ok, that’s like, four words). Fertilizing your lawn and killing weeds should be two separate operations. The majority of weed and feeds target broad leaf weeds. Applying them too close to trees and shrubs will kill non-targeted plants. If this happens, in most cases the outcome is fatal. For what little time you save, it is not worth the risk.
Once you know how many square feet of lawn you have, you need to pick a fertilizer. The numbers on a bag of fertilizer (10-20-0) translate to the percentage of N, P and K. The first number, Nitrogen (N) is for healthy green growth. Nitrogen is the big consumable for lawns. The second number, Phosphorus (P) is for root development. The third number, Potash (K) is a nutrient that we don’t need to add in our black dirt. However adding sulfur to the alkaline soil we have around here will the the lawns. If you have never had your soil tested I do encourage it.
Here is fertilization calculator you may find of use: http://aggie-turf.tamu.edu/aggieturf2/calculators/fertsheet.html
You can find more information on soil testing at these two links: