You just need to make sure that all of the checkboxes in a particular group have the same "name", then make that field required.
For select boxes:
Make sure that your first option has an empty "value". In my example, that would be the Choose State option. Then, make the "state" field required.HTML Code:<select name="state"><option value="">Choose State</option><option value="Alabama">Alabama</option> <option value="Arizona">Arizona</option></select>