Schedule observations so that your science targets are as close as possible to zenith during exposures. Less air mass means less turbulence. One of the AO instrument specialists listed above can assist in filling out the form. Select a guide star near the science target. In NGS mode observing, the guide star must be at least as bright as 12'th R-magnitude.
Brighter stars give better correction.
The formal field of view of the optical system for guide stars is a circle slightly less than 2 arcminutes diameter centered on the science target location. However atmospheric turbulence degrades AO performance as the separation between the guide star and the science object increases. Hence it is best to keep the guide star as close to the science target as possible. It is also a strong function of airmass, with the isoplanatic angle scaling as airmass squared. Observed isoplanatic angles at Lick using the near infrared camera range from 15 arc sec to as large as 40 arc sec.