Overview:
- Estimated achievement difficulty: 9.5/10 to 1000/1000 (6/10 to 660)
- Offline: 42
- Online: 8
- Approximate amount of time to 1000: [35-100+ hours
- Minimum number of playthroughs needed: 5
- Number of missable achievements: None
- Glitched achievements: Killing in the Name: Could require more or less than stated, Amazing Rockstar: completion of Through the Fire and Flames on expert will net the achievement no matter what difficulty other songs were played on.
- Do cheat codes disable achievements? Yes. Basically any cheat that affects performance (rather than just appearance) will disable achievements and saving.
- Does difficulty affect achievements? Yes

Introduction:
Like previous Guitar Hero games, Smash Hits achievements involve intensive playing on the expert career. In order to get 100% achievement completion, all instrument careers must be completed on expert, a band career must be completed, various songs and song sections must be performed well on higher difficulties, and online matches must be completed. Because of the pure difficulty of performing well on expert across all instruments and perfecting difficult sections, this game is a 9.5/10. Without the secret achievements, the game is considerably easier to finish off, though it is still very time consuming.

Note: This road map lays out the quickest and most efficient route to 100% completion. As a result, if there are multiple achievements identical except for the difficulty required, completing the task on the highest difficulty required will net all of those achievements in a fraction of the time.
Any achievement that can be completed locally or online is listed as an offline achievement.

1) Tutorial and Career Playthroughs (15 for 330):
First thing: Complete all four instrument tutorials. If you do not have the World Tour drum kit, you will not be able to get the full 1000.

After the tutorials, start by completing the career with your best instrument. The only song that has to be completed on expert is Through the Fire and Flames, but future achievements will be easier if you play at a higher level earlier on (it takes time to gain skill at the instruments, so pushing yourself to play on Hard or Expert will help you advance quicker). Once completing your first career, move on to the other three.
The completion of all four careers will get you 35 for completing each instrument career (5 for playing, 30 for completion), 4 achievements and 155 for finishing Through the Fire and Flames on expert for all instruments, and 2 for 30 (150 songs overall and Smoke on the Water vocals) for playing through all four careers.

2) Band Career (1 for 25):
Since this can be done with two instruments and any difficulty, it is possible to complete this solo. In any event, it cannot be done online. Simply put vocals on beginner and put it near a fan, and play your favorite instrument. Like always, play on the hardest difficulty possible because more practice on harder difficulties early on can reduce future practice time.

3) 4 Player Band (5 for 85):
All of these can be completed locally or online.

Completing a song with every player on expert will net 2 for 40 (one for completing a four-player song, one for doing it on expert). Getting 100% on a song should not be a challenge on beginner, and can even be done solo (see guide) (25).

There are 2 miscellaneous band achievements for 20. One is for triggering star power simultaneously, and the other is for getting the highest individual score. Neither should be difficult on lower difficulties.

4) Online Play (8 for 145)
4 achievements for 60 will be won by winning a Face-Off match and Pro Face-Off match by 25,000 points (two for each: one for winning and one for winning by 25,000 points). 2 achievements for 65 will be received for winning 50 games (the first will be received after playing 20 online matches). Win an 8 player band vs. band match for 15 (easily boosted). Finally, download a song from GHTunes for 5.

5) Perfection! And Mop-Up (21 for 415)
This will be the hardest part. You must perform very well (often perfecting sections) of the most difficult songs on various instruments… on Expert. There is only one piece of advice anyone can give, and that is to use practice mode. With lots of practice, you will be able to get these performance-based achievements.
The other miscellaneous achievements aren’t difficult to get, especially after perfection. They are self-explanatory, and you won’t have too many left after doing everything else.

Conclusion:
This is a hard 1000. Perfecting song sections on Expert will take hours of practice, unless you can FC (100% notes hit with no break in combo) Raining Blood or Through the Fire and Flames already.

For a beginner, this will take more than 100 hours, the majority of which will be spent perfecting. Even for expert players, hours and hours of practice will not be unlikely.

[x360a would like to thank shocellist for this road map]