In most cases teams are trading up to target a specific player or occasionally a small group of players at one position. The problem with trading now, for example, is that your player(s) may be gone when the turn comes for the pick you acquired. So typically these trades happens as the draft goes along. Sometimes you get fairly certain the guys in front of your target slot won't take your guy. I can remember several times when teams traded up only to see someone trade in front of them and get their guy. That's why teams lie so much about who interests them. The other factor, of course, is that you have to have a team that wants to trade down. They also have to be realistic about their demands. These teams usually make their position known before draft day, but obviously don't typically announce it. Occasionally this is a last minute deal when a team loses the only player they see worth picking at their place in the draft. They all have other targets, but the it becomes a case of how far they can go down and still get a player they really want.
The Cards have done the correct procedure and let other teams know they have an interest in going up. The last minute trade down guys will call them and anyone else who has shown similar interest. Several guys make these inquiry calls, but only GMs or Personnel Directors on the teams that split GM duties, actually make the deals. Sometimes it gets very hectic as the rounds go on as the time between picks shrink. It's all very exciting.
