Time and Effort
I don't think it needs to be said that raiding takes much time and effort out of your day. Organizing and preparing takes a HUGE chunk of this time, while the fights take only measly minutes. With that said Raiding is a TEAM effort, without everyone being prepared and ready to clear content, wipes just happen and the atmosphere just more frustrating and tension starts to build. Remember that when you join a raid (either a pug or a guild run), you have made a commitment of time and equal effort into your character and schedule to kill bosses, just like everyone else. The people advertising in Trade chat spend tedious effort inspecting and checking for how ready you are before going to what should be a successful clear of any dungeon. So if you can't commit the whole way, speak up, I'm sure there is some way to accommodate the situation.
So how do I prepare? Where do I start? Well there are various sources that you can draw from, but many of the things you need to know can be found in game, things that you probably can't find are only a google search away.
- Raid Encounters
Blizzard has made this substantially easier as the game ages. More recent, you can now access the DUNGEON JOURNAL by pressing [SHIFT + J] in-game to review boss abilities, loot drops, and even lore! In raiding, boss abilities are a must know; loot, although you can drool over all day, is nice to know about, but you won't get any until the boss dies anyways, and even then its a slim chance.
Another great source is YouTube, which is one of our personal go-tos for learning new encounters and boss mechanics. Just google a top-guild and the encounter and 10m or 25m. If you're lucky the fight even has the view from your class! Its also helpful to ask people in the raid if you don't know the encounter or let the raid know before hand. Don't wait until you wiped six times to ask questions, ask before the first pull so enough of the kinks are ironed out before everyone gets a headache from simple mistakes.
The two biggest sources of information that you can get about how to play your class are ArenaJunkies (http://www.arenajunkies.com/)and Elitist Jerks (http://elitistjerks.com/forums.php). Obviously, AJ is for PvP and Elitist Jerks are for PvE. The sites are pretty simple to navigate. On EJ, there are compendiums written by pros and top raiders to help theorycraft every class and help everyone maximize their efficiencies in a very constructive way. All the boards are heavily moderated to prevent unproductive posting to encourage an accurate source of untainted information.
So you've read up on all the fights and know the general strategies, you've read through the class compendium on how to play your character, how do you know you are ready?
- Armory Audit
The easiest way to find out is to re-log and check your armory. Click on Advanced, at the bottom there is "Character Audit" that tells you if you're missing gems, enchants, glyphs, or a belt buckle. This may come to a surprise to most people, but you get ONE FREE GEM SLOT if you buy a belt buckle and put it on your waist item which is a great stat boost!
- Gems, Reforging, Enchants
From reading the EJ class compendiums you should already know what to gem and enchant, so make sure that you filled all your slots with the proper gems and enchant all your gear! Reforging is a bit tricky, but using AskMrRobot.com makes everything extremely painless. Just make sure you don't mindlessly use it.
It's important to bring your own buffs to raids to maximize the damage since it can make or break an encounter. Three of the most important buffs you want to bring are food, flasks, and potions. Usually, the best food to bring are core stat boosters (i.e. str, agi, and int), for tanks its debatable, but it seems mastery stam food is the way to go for most tanks. Same goes with flasks, as a DPS you bring core stat flasks, as a Tank you bring Stam/HP flasks, and for Healers you bring Int flasks, unless you are extremely mana starved then I would recommend a spirit flask. Potions are also a great DPS boost: you can use one PER FIGHT, but there is a great way to use two if you use a potion before a pull (which is why countdowns are important!)