Skipping over all the rationale: The hood entrance aperture should overlap your range by at least 3 inches all around, more is better. Once the hood size is selected, compute the aperture area in square feet. Your goal is to have about 90 CFM/sq. ft., so multiply the square feet by 90 to get desired actual flow. This number will be used in the duct calculation, but must be scaled to account for pressure losses in order to specify the zero static pressure rating of the hood (or remote) blower. Use 1.5X as a guess unless all of the losses can be evaluated.

Using the actual flow, choose a duct diameter that keeps the full power flow in the 1000 to 2000 ft/min range. (Divide actual flow rate by the duct sectional area in square feet.) Use the lower end of the range if the duct will get very cold during the winter.

For lowest noise, use an external (wall) or in-line blower and place a silencer in the duct path between the hood and the blower, if it can fit (available from Fantech).

Don't forget make-up air (MUA). MUA is needed to supply air to the hood system so it will actually flow air at the rate that is expected, and to keep the house pressure from falling thereby back-drafting any combustion appliances.

Search this forum on these topics for more information, and download from Greenheck.com their guide and read the first 20 pages or so for a commercial perspective on the issues, with emphasis on cooking plume spillage due to insufficient air flow.
http://www.greenheck.com/media/pdf/otherinfo/KVSApplDesign_catalog.pdf