Question
how do I prepare sandy soil for vegetable growing and get rid of insects

Answer
Hi Gooria;
For insects, read some of my organic gardening answers.
For the sandy soil, it depends on just how sandy it is.
You can till things in to beef up that sand and make it less draining.
Really, with the same things you would do to soil to make it MORE drainable.
Add bark mulch, and in the case of too much sand, I would bring in some good loam and till it in with it.
Barkj mulch tilled in with the soil will help it hold water a little longer, and it will compost and make good soil.
Hardwood bark mulch will compost within a year when it is tilled in, but cedar bark mulch takes two years to compost.
The cedar bark mulch though, repels a ton of insects, so I would use some cedar bark mulch too.
Cedar repels so many insects, including ermites.
How much sand do you have, and how deep does it go before it reaches better soil, or rock etc?
Lets find out more about the soil you have before I suggest how much and what to add.
Dig a hole about 2 ft across and about 1 or 2 ft deep,(2 ft would be best) and fill it with water, and tell me how long it takes for the hole to drain empty.
Then, how dry is the soil? Is it very dry or is it a little muddy?
Charlotte