Somebody asked me for a "consultation" on her first garden recently. This was my advice to her:
1. Pick a sunny spot.
2. Make a raised bed. Buy four 8 foot, 1 by 8's and four corner braces, and screw together a square. Put some top soil in the square after you put it in your sunny spot.
3. Plant only lettuce, from seed, for your first garden. Follow the directions for sowing on the seed packet.
4. Water it every day until you see the little lettuce leaves coming up. Then water it twice a week.
5. Thin out the seeds (pull some that are growing too close together) after about two weeks.
6. Keep weeding and watering until it looks like lettuce.
7. Eat it!
Lettuce is easy and will give you a good feel for gardening. You may need to staple chicken wire around the bed, if you have wild rabbits in your yard.