Here are some notes on preparing for the first tier of raiding in Warlords. It's a long post, but that doesn't mean that you'll have to go to a lot of effort to get ready.
Probably the most "mandatory" activity will be the legendary ring quest, as the ring will provide a significant boost even in BIS gear down the line. You can start it at level 98 by talking to Khadgar's Servant in your garrison. This stage of the legendary quest line mostly involves running some heroic dungeons and acquiring some Apexis crystals, with one raid quest in Highmaul at the end (after you get your ilvl 680 epic ring). Patch 6.1 will likely add additional steps. See this wowhead guide
The next most important job is earning your three extra rolls per week. You can turn in gold, apexis crystals, garrison resources, or honor for these. You can get one free per week with the dwarven bunker, and occasionally another from the Drov the Ruiner follower mission.
As always, you'll want to enchant and gem your gear and bring appropriate consumables. Only weapons, necks, cloaks, and rings need to be enchanted, and gem slots will be less common than in the past. Consumables include flasks, food, DPS or mana potions, and healing potions. Healthstones can take the place of healing potions although they aren't quite as powerful.
Your garrison's follower missions will eventually award a few gear upgrades near the end of the tier. See the cookie-cutter garrison guide
if you want to maximize your odds at these, but keep in mind that the benefit is probably not all that significant, and will probably come in when you're done with progression in this tier or nearing the end of it.
That leaves early gearing. See this chart
for how different sources of gear stack up, and this guide
which contains a slot-by-slot breakdown of gear options. The design intent is as follows:
* If you are part of an organized raid group right from the start, you will want to start in heroic dungeons for 630 gear, and maybe do the daily challenge mode for a chance at 640 gear. From there you can move into normal-mode and/or heroic-mode raiding when they open, and can ignore all of the other sources of intermediate epics. This is the first time we will have an introductory difficulty in the first raid tier, so it shouldn't be as important to be geared to the teeth going in.
* If you are not part of a raid group but want to be, or are playing a raid-ready alt, you will want to look into those intermediate epics so that you don't fall too far behind on gearing.
* If you are only interesting in playing casually and seeing the content, you can go directly from normal-mode dungeons to LFR and skip everything else, including heroic dungeons. Or if you don't want to do LFR, you can progress slowly on non-raiding epics.
There are many sources of intermediate epics. The common theme is that they take a while to get--long enough that organized raiders will likely have better gear from raid drops. Also, most of them can't be warforged or have gem sockets or tertiary stats. They are:
* You can get an item level 640 hat by running the Molten Core anniversary LFR once.
* You can earn apexis crystals through daily quests from your garrison town hall, through garrison work orders, or just grinding them out slowly from level 100 mobs. Apexis crystals can be used to buy item level 630 gear. When Highmaul opens on Dec 2, you can upgrade this gear to item level 645 with more crystals. When Foundry opens in a few months, you can upgrade it again to item level 655 with even more crystals. Apexis gear only exists for the head, back, wrist, hand, waist, and leg slots.
* Crafted epics begin at item level 640 and can be upgraded to 655 and 665 (weapons are 10 item levels lower). These will be slow to make since they use time-limited materials, and you can only use three at a time. They are not bind-on-pickup, so you can buy them from the auction house or make them on alts.
* There are item level 665 BOEs. You can get these from the garrison salvage yard, from lucky random drops, or from the auction house.
* Periodically your garrison will be invaded. If you earn a gold victory when defeating a garrison invasion, you'll get a shot at an item level 645 epic.
* Two world bosses (Drov and Tarina) will become available when Highmaul opens, alternating weeks. They drop item level 650 gear. When Foundry opens, Rukhmar will become available, dropping item level 665 gear.
* LFR will open in wings over time. Highmaul wings of LFR will drop item level 640 gear; Foundry wings will drop item level 650 gear and item level 655 set pieces with weaker set bonuses. Drop rates from LFR should be about twice as high as they were in Mists.
* If you are into PvP, conquest gear is item level 660 in PvE. Honor gear is only item level 620 in PvE.