Companion planting helps get rid of a reasonable percentage of pests, I use a lot of herbs in amongst my other plantings. Also doesn't get rid of the good pests.
A good gardening magazine on herbs will help you out. Will also give good hints on natural sprays which I find do work.

Billy
The reason you have pests is because your plants are stressed and therefore nature hates to see stressed plants (or animals) and will signal.... to the organisms whose job it is to decompose organic matter... to come and feast
When you use an insect poison you are creating a... more stressed system...this encourages more decomposers to arrive for the feast
You have the same proble whether you use an organic or an inorganic poison...just that the organic poison does not last as long...by the way, the inorganic poisons break down, as they deteriorate, into other chemicals called metabolites and these chemicals (metabolites) can be many times more toxic than the parent chemical
In the case of Atrazine (which I am familiar with) the manufactureer has admitted that that some of these metabolites can be 27 times more toxic than the parent chemical (Atrazine)
I wonder what Glyphosate breaks down into
To encourage healthy plants you need to increase the microbial organisms in the soil the plants live in
These microbes interface between the root hairs of the plant and the available nutrients and facilitate the passage of these nutrients (phytomins)
hope this helps
Peter

I agree with Peter whole-heartedly. However, if you are after an organic repellent while you increase the fertility and microbial organisms in your soil, try a garlic spray or organic neem oil. Be aware though that you may be harming or detering a number of beneficial insects.