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

also watering

Once your new lawn is established, you may not have to water it at
all, depending on where you live. In central PA, I haven't watered my
lawn, or fertilized it, or put weed-killer on it, for at least 20
years.

Mow it high with a mulching mower.

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

Right. If you must water, water deep and infrequently, not vice
versa.

vince norris