Tactics”? I think it’s a little simpler than all of that; just trust your gut.
If you’re coming up to a red light, look who’s around and see if anyone stands out. When you come to a stop, is anyone approaching your car? Are they jittery?
Keep an eye on your rear view mirror.
If you’re walking in a parking lot and someone else is there, are their eyes focused on you and are they walking towards you? If you change direction, do they follow?
If in a parking lot and getting out of your car, do a quick scan while getting out to see if anyone is approaching. Do they follow changes in your direction? Basically, are they on an interception course?
While walking around, look behind to see who’s there and again if anyone is focused on you or following. If in doubt, pull into a shop or somewhere safe and see if they pass. What do they do after they pass?
If in a store, is there anyone that doesn’t seem like they belong. Do they seem anxious? etc.
Always have an exit.