With only seven bosses to claim, Firelands is one of the smallest raid tiers we've seen over the past couple of years. I've found that the raid can seem much larger than it actually is due to the massive size of the zone. We're able to explore the terrain and advance in any direction that we please. The first five bosses can be killed in any order, and we fight each on unique terrain. There's also a plethora of interesting trash mobs and mini-events along the way.
Two of the easiest bosses in Firelands are Shannox and Beth'tilac. If you're just starting in Firelands, it's highly likely that you raid will be facing one of these two bosses first. The encounters are very different for healers, at least until their final phases. You'll want to spend most of your time conserving as much mana as possible, as healing against these bosses gets more difficult as the fights progress. Your ability to keep the raid alive will buy your DPS the time they need to finish the job.