Game Room

You only need 6 bronzes medals, but for 6 fairly easy golds, even if you are kind of a mediocre arcader like myself, buy Crystal Castles and Astrosmash and start a Ranked game.
***Edit for those who can't read the achievement description***
You need 2 of each type of medal = 6 medals total. They only need to be bronze medals. Below I tell you how to get all 6 medals while just buying 2 games. For the time medals you replay the game until you get the medal you want. Bronze, silver, gold. I prefer gold myself, but it's up to you what you get.

Crystal Castles ~
~On first screen go to the back of the play area in the corner and you will find a secret jump spot. Press A to jump here and you will immediately get your gold medal out of the way ;)
~ The hardest part is Surviving 6 minutes. For this you need to start a new game, wait til all 3 enemies have come around the corner, then run around to the jump spot and sit there. When the hornets come down about the 5th time they will try to land on you. Run around in a big circle til they get you.Do this 3 times and on the last time use your jump point. Go to the left elevator and go up and wait. Do this again for your extra life and you should just manage 6 minutes.
~ Now just repeat the above til you have 3 shiny golds ;)

Astrosmash ~ just shoot the rocks, the white spinners and the little evil blinking stalkers and dodge from side to side. The 40,000 point gold medal will also net you the Survivalist gold. Repeat for 3 total golds.

This achievement requires paid content.

Medals can only be earned in ranked play, and in games that you either own, are purchasing sessions with using the 40 MS point option, or on games that your console is licensed to (i.e. Someone else bought that game on your console). Medals can NOT be earned in demo play, classic play, or if you are using tokens to play a friend's machine.

There are three medal varieties:
Point Buster : These medals are awarded when you reach certain score targets.
Survivalist : These medals are awarded for surviving a set amount of time in a single play.
Time Spender : These medals are awarded for cumulative game play.

Every game has a Time Spender medal. Note that Time Spender medals can be earned in ranked or classic play, and are cumulative between game sessions. Most games also have a Point Buster and Survivalist medal. Medals "upgrade" as you progress. What this means is that if you have a Bronze medal and suddenly earn a Silver medal, you only have a Silver Medal. This will only count as 1 medal. Bronze, silver, and gold medals all count.

A chart of which games have which medals available, and the goals that must be met to get those medals is posted here:
http://www.tinyurl.com/GameRoomMedalChart

There are 3 different medal types:

1) Point Buster: Beat a preset score.
2) Survivalist: Beat a preset time.
3) Time Spender: Play a certain amount of time.

Each medal type has a Bronze, Silver, and Gold medal. Win at least a Bronze medal of each metal type in 2 different games and this is yours.

----Details about Medals----

1) Point Buster: Beat a preset score.
-Each game has a preset score it intends for you to beat. Play the game, beat the score, and you'll win your medal. If you only unlock the Bronze medal, it will then display the next score you need to win to get to Silver.

2) Survivalist: Beat a preset time.
-Each game has a preset time it intends for you to survive during the game without losing. Play your best, and at the end of your game it will show you how long you played total in that one playthrough. If you only unlock the Bronze medal, it will then display the next score you need to win to get to Silver.

3) Time Spender: Play a certain amount of time.
-This is accumulative of all your play time on one game. Just play the game lots and lots and it will unlock, no matter how much you rock or suck at the game.