That depends upon what frequencies your looking for really. It actually scans quite fast but locking out the frequencies your not looking for can help.
Remember it is really only for close range detection.
I am not sure what you mean by "optimize". Do you mean limit the range of frequencies it is testing? Or do you mean how do you get the best signal strength? Or ???
Signal Stalker only works for signals which are fairly close. You will pick up stuff with SEARCH and SCAN functions long before SS can find it. It's handy when your at the scene of an incident and want to know frequencies being transmitted on. Otherwise, to get the most out if I suggest connecting to an outside antenna.
It has already been mentioned that you need to be really close to the radio for SS to pick up the TX. I recently visited the aiport and saw radio being used. I scanned using SS and voila! PRO-97 detected 451.9 mHz. I go home (about 3 miles) and I could only hear base with rubber duck antenna.