I used Sheldon Browns gear calculator
to set my gears to my cadence.
If you want to pedal at higher speeds you would want a larger (front) chain ring and a smaller (rear) sprocket or one or the other. Do a few teeth smaller on the rear if you need a bit more speed or a larger chain ring up front for more of a change
Your max sustained cadence Vs speed will be the determining factor in gear selection
you pedal at depend on your level of fitness , only you know what your capable of maintaining.
Sheldon Browns gear calculator http://www.sheldonbrown.com/gear-calc.html