Also check your local library for Gaia's Garden by Toby Hemenway. Very useful book.
"High density" planting is a good idea and the book has some recomondations on companion planting, space allocation and so on.
Make sure you have really good soil in your beds. As you build them add mulched leaves (if you can find some now but, add them in the fall) along with manure and used coffee grounds. Make sure that you don't add more manure/coffee grounds than leaves or it will smell bad and that is a bad thing both aesthetically speaking and botanically speaking.
Read up on companion planting on the web and in Gaia's Garden. Some plants benefit eachother and should be planted together and some plants repel one another.
Feed the soil, not the plants.