Rocksmith 2014 Edition

You should focus on doing this whilst hunting all other achievements. This will take a long time, but to speed along the process I have a few tips.
1. Pressing B from the Main Menu will take you to the Press Start screen; sign into another account (local will work). Press B again and switch back to your profile and the missions should cycle.
2. Press the back button to switch to bass before leaving the game. When you return, the guitarcade mission will be "achieve level 1 in X game" assuming you have not played the minigames on bass.
3. Much later into session mode, you will have repeat missions with custom settings. Change the root to E and you can idly play any open string aside from the B string.
4. Playing the Lesson songs count as playing a new song.
5. For the 50-300 note streak missions
A. Blitzkrieg Bop or Black Magic on bass,
B. Blitzkrieg Bop score attack medium on lead
C. Black magic medium score attack on rhythm.
you can play others but these are by far the easiest/fastest

I only did these missions: Learn 1 new song, Session your way for X minutes, achieve level # in X minigame (only if it was convenient) , get a great performance, and hit X note streak.
If I did not get one of these missions I would cycle the missions using the strategy mentioned above.

It is also slightly glitched as I did not unlock this until I had 510~ missions completed. The same is true for the 214 mission achievements.

edit: Devious Jedi pointed out that you can track the number of missions completed in the game hub.
Zoidberg1339 pointed out that the "hit 75%" missions can be easily achieved by doing score attack on easy.

EDIT: The "Remastered" edition now has the in-game stats, where you can track your progress to this achievement!.

MISSIONS are the little tasks and suggestions Rocksmith throws your way.

Do not confuse MISSIONS with 'Rocksmith recommends' (in Learn a Song) and with 'Leaderboard Challenges' in Guitarcade!

There are always THREE ACTIVE MISSIONS that you can choose from.

ONE is connected with playing songs (learn a song or score attack)
ONE is connected with sessions or gear
ONE is connected with techniques and guitarcade

You can see the list of current missions on the main page (when the page first loads up they're not there, but every time you get back, you'll see them in the upper right corner.

Every time you complete a mission successfully, the game will give you a MISSION COMPLETE notification.

It's hard to track your progress, the stats on the Rocksmith page seem not to be working properly. However, TRUE ACHIEVEMENTS actually tracks your progress for you. Just open the game detail or check your position the leaderboards for this game and you'll find yourself. The leaderboard is here:

https://www.trueachievements.com/gamestatleaderboard.aspx?ga...

Some missions stay active until you complete them, others will be replaced every time you load the game.

Some missions will be different for lead guitar, rhythm guitar and bass guitar. Others will stay active even if you switch paths. (Oh, in case you didn't know, you can play bass even if you don't have a bass guitar. Just switch to emulated bass.)

Here are the mission types:
(LaS - learn a song, SA - Score attack)

1)
- PLAY NEW SONGS (usually 1-3) - if you've played all the songs in your game (including DLC you own), the game will stop giving you these. You can switch to a different path and this type of mission wil reappear. (LaS or SA)
- SONG MASTERY (a) - requires that you increase the mastery of a particular song (LaS)
- SONG MASTERY (b) - requires you t increase the mastery of a given number of songs (your choice) (LaS)
- SONG ACCURACY - asks you to reach a certain accuracy percentage (LaS or SA)
- HIGH SCORE ON A SONG - you need to improve your previous score (SA)
- NOTE STREAK - hit a note streak of a particular length. Just choose a song you are familiar with, shouldn't be too difficult. I recommend EVERY BREATH YOU TAKE (The Police) on Bass, so easy and so many notes! (LaS or SA)
- ROCKSMITH RECOMMENDS (LaS) - complete a number of (1-3) recommendations for a given song. You don't actually need to do much. Just start the recommended game or the recommended lesson or riff repeater and quit out. It will count as if you'd actually done it.
- GREAT PERFORMANCE (LaS or SA) - get a 'great performance' on a song of your choice. Actually, you don't need to hear 'GREAT performance'. You can get all kind of evaluation such as 'Brilliant performance' or even 'adequate performance'.

2)
SESSION MODE - asks you to play in session mode for 1, 2, 3, 5, 10, 15, 20, 30 minutes, either with custom setting or with a suggested band. You need to meet the setting requirements - start the session only if all the requirements have the rocksmith guitar pick symbol next to them. If you're only doing this for the achievement, you can use the 'buzzing method' described here (Solution for Mission 214 In Rocksmith 2014 Edition (Xbox 360)) or, if the required session time is too long, just quit out of the game and reload it. The session mission will probably change into a shorter one.

3)
- USE GEAR - just use the required pedal or amp in your setup (this is really fast, the game will stop giving you these once you've tried everything)
- GUITARCADE GAME LEVEL - makes you increase your level in various games in Guitarcade - first asks you to play it, then get to level 2, level 3 etc. Switching to BASS will give you these again from the beginning. The minigames for guitar and bass guitar are separate.
- ALTERNATE TUNING - play a song with an alternate tuning


POSSIBLE GLITCH: The tracking may not be working properly. I unlocked the 214 mission achievement when the tracker said I had 244 missions! The 500 mission achievement came when the tracker said 530. The good news is, that between 244 and 530 the glitch didn't occur again. Again, it unlocked exactly 30 missions after it was supposed to unlock. This seems to be different for every player, though.