Well, there are some GREAT shooters on this board who can offer a ton more wealth on this subject than I can, but I will try to offer some prespective.
The first thing I would say is use common sense. I know that sounds silly, but it is so true. You don't want to pull your car up to a fence and stand on the roof or the hood to get a shot. If I am using a ladder, I keep it folded up and away from the fence until I need to use it. Don't just stand by a fence...I usually stay 20 yards away or so until I need to get closer, then I do my business and go back to where I was standing.
I also do my homework before I go out, and I carry a scanner with me. I use an air-only model, cheap, smaller, and not a threat to police. If The Man rolls up and asks you what you are doing, you tell the truth..."I am waiting for a Sun Country 737 that is flying in from Portland, It will be here at 10:20 and then I am leaving..." Something like that.
A lot of times I will "check in" with someone in authority before I start snapping away. The quickest way to avoid the local law is to head into the terminal and ask someone from TSA
to speak with the duty officer. They can help your or point you to someone from the airport authority. Tell them who you are, offer your ID
, don't make them ask for it. When they tell you it's cool, remember their name. When someone calls you in later and you get a visit, you can say that you already talked to Mr So and So. You go from an unknown threat to someone with a weird hobby.
Also, each situation/airport is different. If you shoot digital, offer whoever is questioning you a chance to look at your pictures thru your cameras LCD
. Know how to use this feature, it is a big help.
Most of all, be respectful. The law is just doing their job. If they tell you you can't be somewhere, find out who to talk with. No police office is going to back down if you start screaming "private property" or "what about my rights."