Try buying nuts in the shell. It takes time to get at the nuts, so you will eat less. If you buy shelled nuts, stick with raw or dry-roasted and avoid the salted, oil-roasted, honey-coated or yogurt-covered varieties.
Stored in a cool, dry place, nuts will stay fresh for several months. Keeping nuts in the refrigerator tightly tied in a plastic bag or in a jar will extend their life, and freezing nuts will keep them good for a year or longer.