Suspicious person contacts
This is probably nothing new to many of you, but I still see this mistake time and again:
When preparing to make contact with a suspicious person, do not grab your mic for the first time while pulling up to him. Instead, radio your intent, location, and physical and clothing description in advance--from a distance--before you approach. That way if a foot pursuit begins or a weapon is pulled, the info is already out. Then you can simply advise "foot pursuit" or whatever you have and dispatch will already have description and location for responding officers.
Not only is this much safer, but it also saves valuable air time if the foo-foo hits the fan as you approach.