Best way to water a lawn ?

I brought a townhome in USA recently.

I am completely new to this plants and gardening.

Outside my home I have a huge lawn with some trees in it.

Since its summer time in USA, I need to water the big lawn every day.

Questions:
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1) Apart from watering the lawn , is there anything I can buy from stores and spray across the lawn
so they are green always ?

2) I was wondering if I could add some other nutrients and spray on the lawn which would cut
down my watering time to the lawn every day ?

3) I know there is no there is alternate for water, but anything else which can help to keep the lawn green apart from just watering it daily ?

You shouldn't need to water it daily. The general rule of thumb is that lawns needs one inch of water per week--this will vary a little bit depending on what sort of grass you have and how heavy your soil is and how warm the weather is, but I'd use that as a starting point. If you're watering for a very short time each day then maybe your total is only an inch a week, but chances are you're applying quite a bit more than that and too much water is just as bad for the lawn as too little water (if your total is an inch a week, you'd be better off cutting back on the watering frequency but watering for longer each time--less frequent but deeper watering will encourage the roots to go down deep which will make the grass a little more drought tolerant). Here's a site with some info on watering for you: http://www.mastergardenproducts.com/gardenerscorner/watering_your_lawn.htm

You'll also need to fertilize in order to keep the lawn healthy & green--you can pick up a basic lawn fertilizer at your local nursery or Home Depot/Lowes/etc. The package will have instructions for how much to apply and how often to apply it. Unfortunately fertilizer won't do much to decrease watering frequency, but since you're probably watering more frequently than you need to now hopefully that's not a big deal!

Here is some additional info from University of Illinois on lawn care.

http://urbanext.illinois.edu/lawntalk/

Hi John, I am in UK but visit USA often, I am more than surprised that your townhouse does not come with a sprinkler system already there, can you check your deeds and what services are included as it should tell you on these papers whether you have a watering systems in place.
I was just thinking that maybe IF you only visit the townhouse you may not have noticed the time that the sprinklers are switched on, they are normally done by using a timer and in Florida, there are local times that you have to use your sprinklers depending on the bylaws of that area, it's worth checking out, can you ask any neighbours etc. hope it's sorted out soon but meantime the advice given will be the best you can work with.
Good luck. WeeNel.

Green lawn is a symbol of proud homeownership as well as a pleasant place on which to relax or play. Watering is a key, and perhaps the most crucial, element in successfully growing beautiful grass. When watering you want to make sure the soil is well moistened. This can be time consuming, but it is better to water thoroughly once a week than to give your garden a brief shower every day. Never use a spray nozzle on a hose; it delivers either too strong a flow or an inefficient mist. The best way of controlling water flow is to use your thumb. Always try to water the base of the plants, but in times of meager rainfall you can give the foliage an occasional spray as well. The best time to water is in the morning. Thanks.

I'm really surprised that in a townhome you have to water your own lawn, out here that's usually included in the HOA fees