Obviously having a ranger with dragon favored enemy would be an nice boon. A would a paladin, since smite evil poops in evil dragons. But I suppose you're asking about how the campaign would be dne?
Since I don't like the idea of slaying dragon children, you should probably avoid making young dragons enemies. Wait until they're young adults at the least. So, what does the arty fight? Wyverns are good. Drakes are also a good choice. There are a number of different types of drakes at various low-mid CRs. To avoid the monotony of killing nothing but dragons, a cult of tiamat (or equivalent evil dragn god) would be a good group of humanoid enemies. Ideally, the BBEG in charge of the cult is an ancient or older dragon. Green would be good, I suspect people din't use green dragons much.
Be sure to step outside chromatic and metallic. Primal and imperial dragns are really quite cool and are spread across the alignments.
If you're using Golarion, make that a cult of Dahak, and use a Blue or Red dragon. Blue if you want a secretive leader (don't know they're being run by a dragon), red if you want them to KNOW.
Alternately, linnorms might be fun, if you want to start high.
Take a look at the 3.5 Draconomicon. It's got some awesome classes, Dragon-Slayer, Dragon-Stalker, Horde-stealer, and Dragon-rider. there's also a bunch of rules for looting dragon bodies and making stuff our of them, as well as items that would be good for fighting dragons.
SO there is a great resource.
I'm jealous. I'd love to play in a Dragon Hunting campaign.
I'd use the dragons as leaders, not solo encounters. Make them almost "bosses" rather than try to fill a campaign with them. Heck, even using good dragons as quest givers and the like could be fantastic in a campaign like this.
The cult suggestion is a great idea. Also, there was a cult in the Forgotten Realms that reanimated Dragons into Draco-Liches and such....that's be awesome for a good extended quest with some tough fights at the end. (Another area where good Dragons may be the ones coming to the PCs and asking them for help to end this desecration).
Early on you could even try some recovery style quests where the group is trying to rob dragons rather than kill them....though it takes a good group of you'll have to TPK them when they mess it up....which could be bad.
I would have there be a prophecy about Legendary Dragon Hunters that will rise. Then the early levels would be about surviving with the Dragons the ones doing the hunting.
Make sure to play up entire villages being destroyed while dragons looked from them.