I think you're looking for crop rotation priciples. This is whereby you grow plants
together which have similar requirements and are vulnerable to similar pests and diseases and then move them about to different beds each season to help prevent those problems getting a good start on the vegetable each season. It also helps to use the nutrients and water more efficiently.
The concept is that you prepare a bed to suit a family or genus of plant
, for example brassicas, which include things like cabbage, cauliflower etc. Once they are finished, the bed will be ideal to use for the solanum family which includes tomato, capsicum etc.
families have different requirements so you won't need to do too much between the crops to prep the soil for the next crop and the pests that affect the brassicas won't be a problem for the solanums. By the time you plant
the brassicas in that bed again , maybe 4 years away, the problems that were there will be long gone. That's the concept anyway. There are plenty of variations within the theme, for example, did you know potato
are in the solanum family with tomatoes. Have a look at the flower
on a potato
compared to a tomato. You'll see a resemblance. You may decide you need a whole bed for potato
though so may not plant
them with the other solanums. But i digress.
Here's a link with a basic four bed rotation system, you can get more involved but this one gives the basics of a 4 bed crop rotation system. http://www.yankeegardener.com/resource/croprotate.html
Plenty of other sites if you google "crop rotation vegetable"
The companion planting suggested previously is more of an accompaniment to these crop rotation principles. For example, in your solanum (tomatos etc ) bed you can plant
some basil. This herb, while not related to the solanums, has very similar growth requirements to these plants
, and is reputed to keep pest insects away, improve the flavour (especially tomatoes) and create a soil level relationship beneficial to the crop plant
. I use these plants
as a fill in where the space allows . Maybe around edges where the crop might be exposed to wind etc. Up to you how you use them really.