How
green is your valley big is your garden? You could either use astroturf (for hassle-and maintenance-free gardening) or use rolled turf. But if you want to see the results of your own labours, then a seeded garden is quite rewarding.
It's a technical art, but in a nutshell, this should help.
http://www.bbc.co.uk/gardening/basics/techniques/lawns_sowlawn1.shtml
Once the seed has taken and begins to shoot, water well and often (but don't flood it) and lay a tarpaulin over the grass at nights (to start with) to keep the temperature in the soil, thus aiding healthy growing.
Once it is established, you'll need to aerate (make lots of 3-4 inch deep holes) and dress (cover lightly and evenly with appropriate sand).
Then watch with horror from you window as your kids/neighbours's dogs tear your lawn to shreds!