Don't negotiate prices until you specify the job. There are now 800,000 lawyers in the U.S., and 60,000 in Canada. Oversupply has put the customer in the catbird seat. With those facts in hand, the logical reaction is to hammer the lawyers' prices down. The logical reaction is wrong.
Specifications are the place to start.
Get monthly billing. But legal work is a hazy brew, and it is hard to see the bottom. You need a measuring stick, and itemized monthly billing is the simplest way to judge if the job is on schedule and the costs are within budget. Don't get monthly billing too often. Most business lawyers would like to know you well enough to send a bill each month.