For major improvements, a remodel, or a similar job that involves several trades, you'll want a general contractor--a construction professional who knows several trades and hires trades people, called subcontractors or "subs" to handle various aspects of the work, such as the plumbing, electrical, concrete and drywall.

Some contractors work with their subs, some just supervise. The contractor is responsible for coordinating and paying the subs and purchasing materials, and generally works on the basis of a firm bid.

Contractors must be licensed or certified in most states; be sure yours is and that he or she carries worker's compensation and liability insurance.