I was really surprised when I got into growing vegetables organically and found out the plant world behaves very much like the animal world. With organic gardening, it is referred to as organic companion planting. There are many benefits to organic companion planting. Two examples are: certain plants protect each other and enhance the taste of other. But it can also be bad to pair certain plants, and these are the pairing to really watch out for.
Marigolds are a good example of a plant that will help protect your garden. The scent of these flowers are so strong that it actually detours certain pests from the area. You should plant them around the borders, as well as various places within the garden. Certain other plants produce natural pesticides.
Other plants help each other. Corn provides something for climbing beans and peas to climb. Pumpkin goes well under corn because the shade the corn will provide protects the plants. In addition, certain plants should not be planted together. For example, tomatoes and cabbage attract the same pest. You can find more information specific to organic companion planting here.
There are many different do and don't s to organic gardening. If you are a beginner to organic gardening, two books I recommend are My Organic Food Garden and Organic Food Gardening Beginners Manual. Good luck and have a great gardening year!