Until last year or so, I never really got into playing a Paladin for some reason and I must admit, of all classes, it seemed like the least entertaining one. I mean, from what I've seen and heard, pala's were jack-of-all trades that could fill in all roles, but not be the best in any. Well I was about to be pleasantly surprised...
Paladin Guide - Leveling
The first levels were a pain in the ass, compared to the other classes and the paladin felt as annoying to level as my druid (up until cat form). Having the druid experience in mind though, I figured I should pull through the boredom and at least try to get to level 30ish to see how the higher tier talents work. I leveled as retribution, which, I was soon to learn, wasn't THE leveling spec. Reading some paladin guide on the Internet, I was tempted to give protection a shot, not only because I haven't tanked with my warrior for quite a while, but also because it was supposedly a good AOE grinding build, when played right. All I can say is that I was surprised how easy it is to grind as a paladin.
I always pictured it as a very slow leveling class, due to the relatively small burst DPS and the hybridness of the class, but I soon stood corrected. I never even bothered going back to retribution, although I've heard people could easily go 1-70 as retri and enjoy it, but for me, protection was way too fun to let go. I figure that if you'd try to level as holy you would have a more difficult time, except if you're into dungeon-grinding (in which case it would be easier to get a spot as a healer).
Paladin Guide - Tanking
When I reached level 70 I already had some experience as a pala MT, but as is the case most of the time, a protection tank will rarely be MT (a job best left to a prot warrior or feral druid), so I had to learn the art of off-tanking. Which, by the way is quite fun: you're equally important to the raid as the main tank, but if you screw up it's not always as visible :P Smaller responsibility for the same recognition? Gief!
One of the main differences I noticed in comparison to warrior tanking is that it's much more important to get hit yourself as a paladin, since your offensive tanking abilities might not have the same impact as that of a warrior (or even a feral druid at that). One of the most annoying things I experienced was tanking a 5-man with a hunter that kept his pet's Growl on auto, despite me asking him several times to stop. As the pet taunted the mob away, I was losing precious TPS from getting hit and it nearly cost us a wipe. That's why, I think it's more delicate to tank as a paladin than a warrior, which is rather straight-forward.
Paladin Guide - Healing
When I geared him up a bit, it was time for some "unofficial" alt raids with my guild and I figured I'd try going holy for a change. I have to say, I had a hard time adapting to healing as a paladin and it was somewhat frustrating at times, since I was used to AOE healing on my priest. Getting stuck on a single target with fast, yet unimpressive heals wasn't my cup of tea. Gearwise I aimed for a lot of +spell crit and intelligence as well as some mp5. Spirit is wasted on a paladin, as you never really have time to regen, your only sources of mana are critting a heal (talent-based regen) and mp5. Intellect is also a desired stat, giving you a bigger mana pool for a sustained fight and adding to your total +spell crit, so you'll have to balance out between these essential stats.
Paladin Guide - DPS
You know how other DPS classes mock paladins and lol about the fact that "palas can't DPS"? Well it's partially true, a retribution paladin will never manage to top a rogue in the damage meters, but I wouldn't say they can't DPS either. Retribution at lvl 70 has some quality burst damage and although it'll go under in a sustained fight (due to lower white damage, mana restraints and mechanics), in a 5-man for example, it can hold its chin up to the other DPSers. I've raided as retribution in 25-mans (alt raids) and despite being on-par gear-wise with the other DPS classes, I constantly sinked down on the meters. It seemed somewhat comparable to playing a shadow priest in a raid environment: you have good burst DPS, however in longer boss fights it won't be enough to keep up and you're mostly trying to support the others than focus on DPS. With the difference that in 25-man instances, shadow priests are essential to have, to recharge your healers' or ranged dps' mana batteries, whereas retribution palas aren't really needed in any scenario.