Capture the Flag
Even if you're not a Druid, you have every right to go and grab that flag. This one should be easy enough to do with a little luck and cooperation from your teammates. You know the drill -- grab that flag and bring it home.
This one is more difficult than the previous one if you play a class with no special means to move around like Travel Form or Blink. This also requires that you travel virtually unmolested, so any attempt by the opposing team to stop you or possession of your team's flag will likely cut your attempt short. You'll just need a little perseverance here. You should probably travel through the tunnels to try and get both speed buffs and pack some Swiftness Potions for that necessary boost. Keep your fingers crossed.
Warsong Gulch Perfection
If you're pugging it, this one is a matter of luck. With enough games played, you'll be certain to get this Achievement at some point as long as you work towards your goals. The good part about this Achievement is that you don't even really need to think about it. It'll just happen.
The only real difficulty about this Achievement is that other players will try to grab the flag, too. Don't think about this too much, just keep trying to capture the flag. If another player grabs it, you can stop worrying about the Achievement and hope you can run for it the next game. The idea here is to keep trying for the flag every game. If you are able to get the assistance of a dedicated healer, the 'not dying' part should be more attainable.
Not In My House
Turtle. That's really the only way this will work. If you have one or two other guys with you, this will be considerably easier. Of course, if your opponents come in full force every time, you should abandon this Achievement and try for something else. It's important to note that you don't need to return the flags yourself, just be around for the Honorable Kill.
Unlike Not In My House, you'll need to return the flags yourself. The good news is that you can do this pretty much anywhere on the map, all you need is masterful clicking skills and a tunnel vision towards the enemy flag carrier. As long as you click fast enough, this should be cake.
Good luck, have fun, and be well on your way to becoming Master of Warsong Gulch!