He'll often start by averting eye contact altogether. Thanks to the marked visibility of our patrol cars and familiarity with even our unmarked Crown Vics, Mr. Recidivist is usually aware of our presence before we're aware of his. At the moment of recognition, he'll suddenly jog in the opposite direction, turn down a side street, or veer his bike into an alley to evade detection. At the very least, he'll deny his peripheral vision as though to will us invisible.
Should we fail to dematerialize and still strive to make his acquaintance, he'll turn on the charm. With a forced smile, he'll inquire about our personal welfare and end every sentence with "sir." (Really, when was the last time you heard anyone with a clear conscience give a tinker's damn about the welfare of a police officer that he didn't know personally?)
Catering to our egos and our authority, he may even say how much he admires the agency we work for. Then he'll flatter us as individuals, saying how we're not like the cops in the next county who'll screw him over for free.
But the dead giveaway that he wants to get away is when he starts to volunteer extraneous information. A simple question about where he's heading will yield a long, convoluted story about a friend of a friend—whose name and address he can't recall—who asked for a ride somewhere he can't remember. Perhaps he hopes we'll forget why we stopped him in the first place.
Should we decide to press the issue, he'll often execute a quick 180-degree turn from being obsequious and servile, to downright belligerent and hostile. (One caveat: If he's openly hostile and baiting you on the front end, he's probably not good for anything right then and there and is reveling in the fact that you don't have a damned thing on him.)