Other things:

(1) Don't let them plumb the main drains directly to the skimmers. Plumb each set of main drains together and run a dedicated line back to the equipment. Each skimmer should have a dedicated line run back to the equipment.

(2) Make sure there are enough returns/inlets to the pool. You may need six or more. Perhaps others can chime in here.

(3) Make sure they will provide you with evidence that all contractors performing work on your property are covered by insurance.

(4) Make sure they will provide you with lien releases (lien waivers) from all contractors and material suppliers, in effect indicating that they have been paid.