Overview:
-Estimated achievement difficulty: 4/10
-Offline: 49 (1050)
-Online: 20 (440)
-Approximate amount of time to 1490: 30-40 Hours
-Minimum number of playthroughs needed: 1
-Number of missable achievements: 0 (Replayable missions)
-Do cheat codes disable achievements?: Cheats available after 100% sync on specific memories. Does not save game progress while cheats are on.
-Does difficulty affect achievements?: No
-Glitchy achievements: "Sage" was glitched from an update, but another update fixed it.
-Unobtainable achievements: None
-Extra equipment needed?: Online Pass which Ubisoft calls Passport. This is for multiplayer. If you buy the game used, you likely won't get the code inside. Also there are 3D glasses but they are not required for anything.
Introduction
If you have played any of the previous games you will be familiar with what's going on for the most part. If you have played Assassin's Creed Brotherhood, then you are in luck. Not much has changed. Even better is that the achievements are easier, specifically in multiplayer. You won't even have to boost anything. Like usual, there is no difficulty in this game. But it's very easy. If you die you restart at a checkpoint of sorts. You will now have bombs at your disposal making the game even that much easier. The collectibles have been changed up. No longer must you collect feathers, but instead data fragments. They literally just take the place of the feathers but work the same way. Collecting 50 nets you the map for free for the rest of them, making collectibles in this game need no guide! Once you beat the game, you are able to free roam the city and play any memories from DNA that you wish. Nothing can be missed.
Step 1: Playthrough Until Sequence 4 Memory 3
What you need to do is buy every shop you can while you move along through the memories. This will help build your money up. The more you buy right away the more money you will have later. Time is literally money here, as the more shops you own the more money that goes in your bank every 20 minutes of game time. Also take over all dens and recruit as many assassins as you can, sending them on missions to gain experience.
By the time you get to the listed memory, most of the districts should be unlocked. You can spend your time finishing up the Assassin Missions (to gain them to Master Assassins) and doing other misc achievements. Remember to use Eagle Sense while you do missions so that the Data Fragments appear.
Step 2: Complete Rest of Game
By this step you should have obtained many more achievements. You likely spent hours and hours building up your assassins and trying to do other achievements. You should also have a huge supply of money which you should save for buying books later. Once you hit Sequence 5-3 you will want to snag all of the Memoir Pages because by then you should have been able to buy the map if you were collecting Fragments (needed 25). Also you can do the Desmond missions on the island by selecting it in the start menu. During Sequence 7 you'll be able to go to yet one last place to finish everything you couldn't do in previous sequences. You can of course do everything after you beat the storyline, as you will be able to free roam and do any other missions you want again in the DNA menu.
Step 3: Mop Up
This should be your favorite step. It means you are completing the last few things you didn't complete yet. Most likely this will be in the form of collectibles or buying the rest of the over priced books. If there's any other misc achievements you need, you will be doing them here. Also you can replay any memory to get 100% sync on it if you haven't been getting them anyways.
Step 4: Multiplayer
This is an extremely easy 200 points. You could have done this right away if you wanted to, before playing the campaign. Get to level 20 while playing each game mode at least once. That's basically all you need to do, because the other achievements should come along the way. If for some reason they don't refer to the guide for more details. Escort is the easiest to get points. You'll also want to work on the achievements for the 2 mulitplayer DLC (Mediterranean and Ancestors) for the added 240. Boosting parties will go a long way in speeding these up.
Step 5: Lost Archive DLC
There are 7 new memory sequences. You'll get 5 story related achievements on your way through the levels. You should also go for the "Save Yourself" achievement, which is very easy to get. You may even get it by normally playing, as there are many possibilities to fall down really far.
Be on the lookout for the decipher fragments in every memory. It's possible to collect all 20 fragments on our first playthrough.
Search for the remaining decipher fragments if you haven't found all of them before. You can select every memory through your DNA-menu. Go to memory 5 when you've collected all fragments for "Breaking to Loop". The last 2 achievements will probably be "Impress Warren Vidic" and "Cross Styx without Dying", as you will probably fall down some times on your first playthrough. Just memorise the levels and be cautious.
Conclusion
This set of achievements were easily obtainable. They could have been so much worse. You could have been required to prestige a few times (or 99 max level). You could have been made to get 100% sync in the entire game. You could have been required to do a lot worse, but you weren't. You were able to play a very enjoyable game and get pretty easy achievements along the way.
[x360a would like to thank Tyger7 for this Roadmap]
[x360a would like to thank ShadowStefan for Step 5 DLC contribution]