As a ranger, it would be wise to focus mainly on Ranger elite skills at first, and then go on to other secondaries which could be useful to your character.
The wiki page here,
http://wiki.guildwars.com/wiki/Ranger_elites has a list of all the Ranger elites. Click on the links to see where you can access 'em. Have a look at that list and sort out which ones belong to the campaigns you own, then look at their description and see if they sound useful to you. Some elites are more useful than others, but the majority do tend to have a use.
Ranger elites that I personally like to use include Crippling Shot (Prophecies), Punishing Shot (Prophecies), Heal as One (Factions), Broad Head Arrow (Factions), Prepared Shot (Nightfall) and Magebane Shot (Nightfall). I'm sure other people will have their own favourites and even loathe some of mine. But hey, that's how it goes ^_^.
Remember, you can pick up more Signet of Captures from Skill Trainers for 1 skill point and a varied amount of gold (which goes up to a maximum of 1k) so do try a few out!
