I use ZED Web every time I go to work as I have to. Two flights to get to LHR and the first and second leg of each return trip is with another carrier and not my own (BA). ZED Web is very easy to use. All you have to do is list yourself on the flight you want to travel, add your personal data and write down the FLYZED listing identifier number, which you have to present at the airport.
In my experience, it's all down to availability. If there are more than 20 seats available, they'll give you a boarding card. Otherwise you have to sit at the gate and hopefully get a seat there. It's really easy so don't worry!
All airlines use the same terminology.