Guitar Hero: Aerosmith

Alright, you can either earn this achievement by playing every song with a buddy, or, you could turn on the no-fail cheat and play every song by yourself.

1. Select "Options", "Cheats", "Enter New Cheat" from the Main Menu.
2. Strum each note or chord to unlock "No Fail" Mode.
3. Pressing G from the "Cheats" Menu will disable this cheat.

G + R, B, G + R, G + Y, B, G + Y, R + Y, O, R + Y, G + Y, Y, G + Y, G + R

Make sure you play a few notes on each instrument, for good measure.

EDIT: You should probably include to go to Multiplayer > Co-op in the guide considering half the commenters are confused about this.
For what it's worth, I did NOT have to do this in one session, I did NOT have to hit any notes on EITHER controller, and I did NOT have to keep both players on the same difficulty (The Elven Jedi's solution, while confusing, is correct). I did have to turn the cheat off and fail a song -- this last step should be in the guide, not just the comments.
Posted by Mental Knight 5

To add to the previous solution, both players must be on the same difficulty and each controller has to hit at least 1 note in each song for it to count. then back out after you finish the last song in the last setlist, disable the cheat, then re-enter co-op and fail any song.

The glitch with the "No Fail" Cheat really works. Just pick each song once and let it finish.
NOTES:
-You do NOT have to press a single note.
-The song does NOT have to be viewable in the history (marked with stars and score at the right of the song).
-You must pick the song TWICE if you also want to do this with BOTH INSTRUMENTS, just once be Bass/Rythm and once be Lead.
-Pick the SAME DIFFICULTY through the whole career for both instruments to not make it confuse.
-After playing through each song, FAIL ONE SONG (without the "No Fail" Cheat of course) to make the achievement pop up.

with regards to bmlx's comment, so nobody worries, both players DO NOT have to be on the same difficulty.

only the person who is the "least" difficulty has to remain that difficulty throughout the setlist, for example: my friend was playing easy bass and I started on expert guitar and I could go to any diff. no problem. if she changed difficulty however, then the song history would be gone.

now I can't say if the "worse" player played on med. or hard lets say and went down if that would work but I doubt it... I think the "lesser" player needs to stay the same. but it should be pretty obvious -- if the song history is still there then you're good to go.

Many have doubted whether or not this achievement is obtainable over Xbox Live, and after trying this method myself, I can say that it IS possible to get over Live, but, and I stress this, ONLY THE HOST WILL GET THE ACHIEVEMENT.

I was unsure as to whether the achievement would work or not, but I set up a few sessions as a few friends swore they got it this way. Anyway, the boosting method is as follows:
- Whomever is going for the achievement first, should set up a private co-op player match, 7 songs. Send the other player an invite, then when they're in, the host chooses the first 4 songs, the other player the next 3. Complete the songs, then repeat 3 more times. Once 28 songs are complete (4x7 song setlists), set up a 3 song match, with the host choosing the first song and a random one, and the other selecting the last song. The achievement will unlock for the host after all 30 songs have been completed.

This method will net you both Love Me Two Times and Deuces Are Wild in ~12hrs of play, as 4 playthroughs of the set-list are needed (2 per person, per instrument).

I'd like to thank Stealther GodX and Ultima22 for helping confirm this method, although to their annoyance as it ended up with them not receiving the achievement first time through.

So there's been a lot of guides and comments over the years, I just want to simplify this for all users who need "Love Me Two Times" and "Deuces are Wild"

*** You can use 2 regular controllers (Guitars NOT NEEDED at all)***


Step 1: From the Main Menu; Select "Options", "Cheats", "Enter New Cheat"
Step 2: (a) if you're using a guitar, strum the following notes as listed
(b) if you're using a controller, you MUST use the buttons & left stick to strum the following notes listed below

(Guitar): G + R, B, G + R, G + Y, B, G + Y, R + Y, O, R + Y, G + Y, Y, G + Y, G + R
(Controller)
LT & LB, RT, LT & LB, LT & RB, RT, LT & RB, LB & RB, A, LB & RB, LT & RB, RB, LT & RB, LT & LB

*Game will now say cheat unlocked"; make sure you turn it on

Step 3: Head back to main menu then go to "Multiplayer", "Co-op"
(Don't worry about characters, costumes, venues, etc. will not effect you from getting the achievement; MAKE SURE to select the same difficulty for both controllers)

Step 4: Play each song in order TWICE (once as the Guitar "lead", once as the Bass "rhythm")
(I played at least one note for each controller during every song)

After about 4-5 hours you should have completed every song TWICE from "Dream Police" to "Train Kept a Rollin"

Step 5 & 6: After the 2nd play through of Train Kept a Rollin'; go all the way back to the main menu of the game and go back to "Options" disable the "No-Fail" cheat.

Then go back to local co-op multiplayer (i.e. Step 3) and select "Train Kept a Rollin" and fail it (press all the buttons once the song starts to speed up the process of failure)

You will pop both achievements at the same time

hope this simplifies things for you