This is how it works. There will be 4 rounds, in the following order: Head Coaches, Offensive Coordinators, Defensive Coordinators, and Special Teams Coaches. In each round, the only teams that are picking are the ones who need coaches at that spot. You can fire a coach to create a spot in order to enter the draft if you would like to. In the first round, teams may select an offensive coordinator, a defensive coordinator, or a special teams coach who is employed by another team to be their head coach. The team who currently employs the coach is allowed to choose to match the offer, and therefore make the coach in question become their head coach (they cannot match and allow the coach to remain in the same position). If they choose not to match, they receive the 3rd round pick of the other team (If the other team does not have their own 3rd round pick, the other team would receive the highest 3rd round pick of the other team. If the team has no 3rd round picks, the other team would receive a 2009 2nd round pick). However, to prevent teams from entering the first round, making an offer to someone else's OC, having the other team match then just keep their HC therefore hurting the other team, you must have an open spot at the position to enter the draft. So if I wanted to try and get Tom Moore to be my head coach, I would have to fire Joe Gibbs first. Anyway, if I lost a coordinator through the draft (recieving comp, or promoting a coordinator to head coach), my team would then be entered into one of the later rounds for a coordinator spot.
I understand this is slightly confusing, so feel free to post any questions in here.