The good thing is, once you've made your Paladin, you will log into the game decked out in epic gear, the Merciless Gladiator's Redemption, along with matching Veteran's Ornamented pieces and other healing items. If you don't like the standard issue equipment you start out with, you can check your bags for two more sets of completely different gear: the Merciless Gladiator's Aegis and Veteran's Lamellar items; and the Merciless Gladiator's Vindication and accompanying Veteran's Scaled pieces. If you want to tailor your gear a bit more, there are equipment vendors that sell some PvE raid items such as the Eye of Gruul or Dragonspine Trophy. You can mix and match items from a wide selection to tweak your gear to your specifications. Later on, you can also purchase gems and enchants -- conveniently bundled into usable items (a sign of things to come for Enchanters, perhaps) -- to personalize your Paladin for the TTR.
A world of Arena
The unique thing about the TTR, of course, is that it's dedicated purely for Arena play. So while players may make a Paladin to try out the class, it will never be the complete experience. There are no mobs, instances, nor quests. The TTR, and presumably the tournament server when it finally goes live, is designed to cater to Arenas so this must be taken into careful consideration when designing your Paladin.
All newly-created characters on the TTR have their talent points completely available for distribution. Since it's an Arena tournament realm, all talent choices should be geared within an Arena paradigm. In this regard, the Paladin's Protection tree will serve mostly as source of support abilities rather than as the primary build. We're then left with a choice of whether to go Holy or Retribution (or Holy with Retribution support, the so called Shockadin). Players who wish to experience tanking with a Paladin are flat out of luck on the TTR, and with the current firestorm about Paladin tanks, the best way to learn that aspect of the class is probably through playing it from 1 to max level. Oh, and tanking endgame. So let's, uh... move along.
Chris has already written up an excellent guide to speccing for Holy PvP, I'll just reinforce the idea that some talents will be completely useless in the tournament server, such as Improved Lay on Hands. For example, half of Fanaticism's effectiveness on the live servers is the passive threat reduction. Some players don't use Judgements to deal damage, but to exercise some control (e.g. - Judgement of Justice) so the +crit isn't as important. He also mentions that Improved Blessing of Wisdom is good as a filler talent, which is true, but some players might also want to consider taking points in Pure of Heart, as additional protection against Curse of Tongues, which is a real bane for a class without any instant heals. If the improvements on the PTR go live in Patch 2.4, Holy Shock becomes a much more viable option for both healing and an offensive spell in a pinch. If you're taking points in Protection (if you want to heal your team, you should), make sure to pick up Guardian's Favor and Blessing of Kings. Chris already mentioned the mitigation aspect of BoK, but there's also the all-important increase to Stamina for your teammates (and their pets... don't forget to buff them, too).
Go over your gear
Make sure that you're happy with the gear you have. For some players, the provided gear is an upgrade from what their characters have on the live servers. For others, the gear isn't much better, particularly for hardcore PvP players who have Season 3 gear. What the tournament realm offers, however, is gear parity. With all players having access to the virtually the same gear, equipment discrepancy in match-ups is almost eliminated. I say almost because it's possible to make choices that put you at a disadvantage in an Arena scenario. Because the gear vendors also offer raid gear without Resilience, it can happen that gear choices will gimp you for combat.
There are other, curious gear options by default, particularly Retribution Paladins, who are given Merciless Gladiator's Painsaw as a starting weapon. If you plan to go Retribution for the TTR, or Arenas in general, it would be wise to visit the weapon vendor and pick up a different weapon. There are excellent alternatives available, and I would recommend picking up the Twinblade of the Phoenix. While you'll miss out on the Resilience from the other Merciless Gladiator two-handers, you'll have a significantly higher top-end as well as sockets for further customization (you can throw in three Mystic Dawnstones if you miss the Resilience). Besides, it's not everyday you get a drop from Kael'thas off a vendor.
If you opt to go healing, consider mixing and matching pieces of the Aegis and Redemption sets. You won't particularly need the 4-piece bonus which is 10-second reduction to the cooldown of Hammer of Justice. You will benefit more from stacking two +35 Resilience bonuses. Your raw +healing will take a hit, but you can make up for it with enchantments and gems. A +healing of about 1500+ will be good enough to give your Holy Lights some kick, though some players prefer topping off at 1800+. It's entirely up to you, which is where player strategy kicks in. An important note about Resilience is that in Patch 2.4 it will also reduce mana-drain effects, which has proven to be one of the most effective ways to neutralize a Paladin in Arenas. Once you manage to hit 493 Resilience, you've maxed out on the mana-drain reduction, so you can beef up in other areas.
Gem choices are interesting ways to personalize your Paladin. For either Holy and Retribution, I personally prefer Powerful Earthstorm Diamond. The Stamina certainly works towards survivability, and the stun resist works towards freedom from control. Aside from Stoicism, Paladins have no other sources of stun resistance on the TTR. Mystic Dawnstones will always find some use, as well as the oft-maligned green gem Steady Talasite. Others prefer to go for pure stamina with Solid Stars of Elune. Play with what you feel comfortable with. The good thing about the TTR is that everything is free. Well, practically free. You actually have 5,000 gold to play around with, but all you really need to spend on are a few items. If you ever run out of cash, a goblin is available to top you up again. So feel free to experiment with the right balance of statistics. Socket and re-socket items, enchant and re-enchant them. Find what works best for you.
Play with your Paladin
Creating a Paladin on the TTR is an excellent way to play around with talent specs without actually having to spend on them. If you have a Paladin on the live realms, a Paladin on the TTR can be customized and tested through duels or Arena battles before you apply what you've learned on your real character. The TTR frees you from many restrictions that may be in place on the live realms, not least of which are probably gear. You can even, on a whim, delete all your characters and re-roll the same ones with slightly different hairstyles. If anything, the TTR offers players a chance to play around with any class.
The long and short of it is that I highly recommend getting on the TTR and creating a Paladin. For those with Paladin characters, the TTR offers a refreshing do-over. For those who have never played a Paladin, having the ability to create a max-level one decked out in epic gear can be a pretty good experience. It certainly won't substitute for actually learning the class through 70 excruciating levels, but it gives a good primer for those who would like to try the Paladin or are considering rolling one. It can also give a good perspective for Arena players who have Paladin teammates and would like to understand what it means when their teammate groans about losing them in Line-of-Sight of healing or getting locked out of their one and only school of magic with a well-timed Counterspell.
While the TTR can be a lot of fun -- and Blizzard seems to have upgraded their hardware to prevent earlier issues of lag -- I think the live tournament realm will be even better. If you don't have a Paladin but would like to play one in the upcoming tournament, then head over to the TTR and build one. Get some practice in and hopefully fall in love with the class. I know I have.