Dragonflies are somewhat territorial, and will often fly back and forth within a certain defined range. They will often stop and hove for a second or two near the end of that range, before heading the other direction. That is the best time to shoot them. I was using AF about half the time.. and manual focus the other, but you have to be fast. With a little practice.. it isn't hard. At this particular site, there are a lot of cattails and cane that form a "wall". This dragonfly was flying between me and the "wall".... so his flight was a little more restricted than normal as he couldn't fly out over the water, that helped a lot. When ever another dragonfly would invade his space, he was chase it off and then hover again.. to see if it was gone, giving me more opportunities to get shots. Hope that helps.
Haven't tried shooting gulls.. although I tried some swallows the other day. That was impossible... little guys are fast and totally unpredictable. I will have to work on a way to shoot them. I did get some decent Magpie shots the other day, flying.. but the distance was a little more than optimal.