I know that's vague, but different plants require different types of soil. Some like more acidic soils, some are middle of the road types. VERY few like wet soils.
If you use compost, make sure it's well composted compost. Otherwise it will tie up the available nitrogen in the soil while it continues to decompose.
Sand really will not do too much to improve the drainage unless you add much more than you think you need. At lower quantities, sand actually decreases drainage. It takes a lot to increase drainage with sand.
I usually try to avoid amending soil unless it is a large amount of bed area. Amend it deeply too, as deep as possible. If you amend only a small amount of soil, you will not help the plants much in the long run since they will only want to root in the amended areas.