How does the upgrade system work?

I'm *A Gold via BD and by the looks of it will do quite a few jumps between Europe and North America in jan - march which will render me elite with AE (I think AE program is better) by end of march.

Can I use my *A Gold to request upgrades?

I flew KLM a lot and have been gold with them for the past 3 years but losing it now. Once in all the times I've asked have I been upgraded on request. One op-up, one on points and NWA upgraded med when I was delayed in to Detroit and they realised they'd forgotten to reschedule me on a later flight to Orlando. By then Y was full and when they noticed my elite status with FD (at the time) gave me a seat in first.

I've never asked at check in. Always at gate (until I gave up as I was always turned down) and was also told at gate to check with flight crew (and that never works. Was rather rudely told I need to be a member of their FFP and use miles or have elite status. I was wondering what part of "I am gold elite" she didn't understand but never said anything. Y was chock full and C was wide empty)

So, anyway - how does it work? I keep reading a lot about people being upgraded with no voucher, nor are they using miles.

The one thing I have understood is to not book a special meal.

/E