The key to domination on most maps is just get to B first. Once you've got it, on most maps, it's very difficult for the other side to 'turn it over'. At that point they then have to try and get both A and C, which again, on most maps isn't feasible as they're too far apart to hold both for long. As soon as you have the two flags you can just go into defensive mode and hit any one of a number of sweet spots around the flags that you hold.
The worst team I ever played on was on Crossfire. We'd just taken A and then all headed up to the end of the street. Suddnely I turned to head down the map and the rest of them turned and took up residence in the sniper building. I carried on playing, but just slipped into 'cynical' mode. I hate doing it as if you're not holding two flags then really to me, you should be trying to get at least one of the other two. In this instance though, I didn't see any point, it was only ever going to end in me getting an ass-kicking. Needless to say, all of those players are now 'avoided'!
I enjoy domination, and headquarters for that matter. I don't mind TDM either, and Groundwar is usually absolute carnage. The only thing I don't like about Groundwar is that it's usually a case of you shoot someone, and then someone shoots you because there are so many people running around the maps. The best tactic that I've found for Groundwar is to just use a 'stealth' configuration.