For me personally, I am friendly. Ask how their day is, ask how busy it has been, depending on the time of year happy new year ... and small talk about the area.

Last guy I had when coming into the US used to be a software developer as well (Fortran, Cobol, and Pascal) and was interested in what kind of work I was doing.

Haven't had an issue yet. I am on a green card, and even-though all my paperwork is in order I still find myself nervous while waiting to enter the US. Also, the whole fingerprinting/picture taking makes me angry and I feel like I am being treated like a prisoner rather than a tax paying citizen.

Say as little as possible. Speak clearly. And if entering the UK, have a bank statement with you. They like people with money (this is not something I made up, it's in the immigration rules, called "maintenance").

If you have no money then you may be there to make some (is the thinking).

If you can show you have enough money to support yourself and get out again then it will make your life easier. However they will already need to be suspicious of you to take an interest in this.

From what I've heard, Australia does the same and so do a few other places. The question is often framed as "and how much money have you brought along for your holiday?", which is doubly loaded as there's a right answer and two wrong answers (nothing and X, where X is bordering on enough to kick start a new life). Immigration sucks.

Australia has an actual dollar amount (AU$3000 I think) that you have to have before getting a one year work visa. A friend went there recently and that was his experience.

100 bucks a credit card :)

I'm allowed into Oz with as little or as much cash as I like, for the next few yeas at least, which is quite nice.