School of Hard Knocks

It might be nice to explain to those with NO battlegrounds experience what the objective is a bit more step by step. Rate this up if you have no BG experience and you want to know more about what to do. This is not going to be a /rant to nerf the achievement or a /whine how hard it was or a /brag how easy it was. Also for starters, don't mount when you have a flag or you'll lose it. [ETA: new edits marked below.]

Capture the flag in Eye of the Storm:

In summary, the objective is to click a flag and return it to a base owned by your faction. There are 4 bases (2 each by the Alliance/Horde entry points) and a center flag placed on a mound on sort of a bridge, so don't fall off. Everyone will need to run to the center obviously to click the flag (it'll have a cog/gear tooltip). The flag takes like 10 seconds to attach to you when you click it, like a cast. You cannot be in combat or else there will be an "Interrupted" message. If you are successful, a message is broadcast "[Your name] has the flag," or something similar. Nothing will go into your inventory; the flag just appears on your back so you know if you have it! That is, if you are lucky enough to get to it, because there will be traps, rogues, AOE everywhere on that center mound. But at some time in EOTS (for me, 4 BG's) that mound is going to be clear--AND you will see a message broadcast "The flag has been returned to the base" or something like that. Hopefully you'll be in the right place at that time, and hopefully with a base owned by your faction to run to.

My advice is to just try to keep that center mound clear of the opposing faction, and try to be first to click it while everyone is elsewhere, and be patient. Once you do have the flag, you have to make it to one of the 4 bases, as long as it's owned by your faction. If you're NOT the first to click the flag after it respawns, but someone of your faction IS, then protect the heck out of them. I put Aspect of the Pack on, and lay down traps for my flag carriers, and Flares if they were up. [ETA: Ok, it's obvious I do not do BG's, because maybe Aspect of the Pack will get a bunch of people Dazed. No one yelled at me, but no one engaged us either.] Eventually, the opposing faction will kill an unlucky flagbearer and the flag'll be on the ground for you to pick up and click. Then, when you are successful, hopefully you will run right for your base and the minute you land there, you should be done. Look at your Achievement tracker and your EOTS should be cleared off.

Assault a tower in Alterac Valley:

The objective here is to find a tower owned by the opposite faction, run to the top of that tower, and click a banner inside. (Again, cog/gear tool tip and about a 10 second cast time and you can't be in combat to click the banner.) Initially, there will be 4 each Alliance/Horde towers. What do the towers look like? I was expecting a tower, but they're not towers really. The Alliance ones look to me like the lookout stations in Loch Modan (we've all done the Tunneler's Ear's Quests) and the Horde ones look a little like the Orcish towers in The Barrens where you pick up Harpies Threaten. Anyway, at the top of these towers are some NPC's guarding these banners. If you're lucky, you can run past the NPC's and click the banner if you're in a group, but if not, try using your pet for classes with them. I've done this twice and both times my group's synergy got me this prong of the achievement. One person was dual boxing with a horde/alliance toon, and the alliance person organized everyone's achievement at the tower using his hordie to help click the flag to make it a Horde flag, just so we could turn around and reclick it and make it an Alliance (for as long as he could, anyway--someone on the Horde didn't appreciate the help as you might imagine).

The thing everyone is saying about this is kind of true: everyone of the other faction is running past you and not wanting to kill you; if they have their orphan out, they probably are looking for a tower guarded by your faction's NPC's and don't care about you. But because of the layout of the map, you're trying to go past YOUR territory into THEIR territory, so you will cross paths with quite a few of the opposing faction so just try to be speedy and use the posts here that contain the maps of the bases if you don't know how to read your BG map.

Assault a flag in Arathi Basin:

I'm a little bit fuzzy about what I did to get this but I'll edit this tonight when I do it on my alt. If I remember correctly, there will be 4 bases you need to capture, and each base starts out neutral (ie., with a grey non-Alliance, non-Horde flag). I think once you touch a grey flag, it takes about 10 seconds of cast time, and if you are the first successful person to click the flag,the flag becomes that of your faction. [ETA: But you won't get this prong of the achievement met! You can only click on the flag of the OTHER faction to get it met. Grey is not good enough in AB.] Like the other two above, you cannot be in combat or else you get an "Interrupted" message. And like the other two, there will probably be three or four people trying to click the flag so you may not be first, so be patient.

ETA: For patch 4.3: This one I got on an alt today and I had to click the opposing faction's flag. I came in with my /beg and my /help emotes to the one defender that was there. It seemed as if the defender was going to let me have the flag, because he wasn't casting any spells. Meanwhile I was saying "I need a flag for my orphan, so please let me have one!" in the /bg chat. Just then, the defender started to get ganked by a rogue and I just did a Hail Mary and clicked their flag.

Return a fallen flag in Warsong Gulch:

I'll confess I didn't know what to do at first, but it's really easy, in theory. First, someone of the opposing faction has to take your flag from your base and begin to run it back to their flag room. You'll stop them by killing them, and the flag will be on the ground for you to pick up. You'll pick up YOUR OWN faction's flag and voila! Ignore their flag, because if you try to be a hero and run their flag to your base, you won't get the achievement. A lot of ranged classes might have problems with this if there is stiff competition and scads of orphans running around the dropped flag. With good communication, hopefully you will be in an understanding BG group and help each other out. Doing this, everyone was rooting for me and helping me, and was a really positive experience.

Hope that helps. Remember to rate up if this helped you figure out what you were supposed to do. ETA: I don't think anything has changed in 4.3.

Blizz took the opportunity to continue to ruin two different facets of the game yet again this year. PvPers get their BGs ruined for one week, and achievement hounds get to face the realization that an entire year's worth of work has been made wasted for most people. I set a goal for myself late last year to get seeker and finish all holiday titles (with the mount and master riding). Safe to say this lone 10 point achievement may stop me from reaching my goal. I don't play WoW for PvP; in fact I detest PvP. My gear doesn't have resil on it for a reason. Don't get me wrong, I will try. However, I don't know anything about any of the battlegrounds, and after doing it for some today it's clear the "pros" take pleasure in preventing the rest of us from getting this achievement. PvPers QQ about stuff like this, and I support them. They don't want cheev hunters in their BGs, and frankly I don't want to be there. But for some reason Blizz insists that I spend hours and hours dying and rezzing just to "try" to get an achievement.

I'm profoundly disappointed that Blizz would make an achievement that another player can actually prevent you from getting.

There are a lot of great things in this game, but this is perhaps the lowest point in the entire affair.

There goes all hopes of getting a Violet Proto Drake...