- Estimated achievement difficulty: 4/10
- Offline: 44 
- Online: 0
- Approximate amount of time to 1000: 25-35 hours
- Minimum number of playthroughs: 1
- Number of missable achievements: 4
- Do cheat codes disable achievements: No Cheats
- Does difficulty affect achievements: No Difficulty
- Glitchy achievements: "Disciple of the Creed" [see achievement guide for more info]
- Unobtainable achievements: None
- Extra equipment needed: None
Assassin’s Creed does not have very difficult achievements, but there are a lot of collectible related achievements that can be quite time consuming. There are also a few missable achievements that this roadmap will prepare you for. As long as you are aware of all the achievements before going into the game, you should be able to 100% this game with a single playthrough. There are three main cities that you will visit three times each. In your third visit to each city, you will rack up the achievements quickly. You should be aware of http://www.assassinscreed-maps.com/, as using this site will make your job infinitely easier.
Step 1 – Missable achievements – 4 
There are four missable achievements that you need to be aware of before you begin the game. This is an open-ended sandbox game, so all the others can be completed at any time, even after beating the game, but these four take constant vigilance through your entire playthrough.
- "Hungerer of Knowledge": Your first memory glitch comes in your first memory, and every ensuing memory. I got lucky with this one on my first playthrough and got it during my final assassination. Just watch very carefully at every cutscene.
- "Conversationalist": This is the easiest to miss. I missed this on my first playthrough, and still have no idea where I missed. Just make sure that you talk to Lucy over and over again until she tells you to go lie down, every time you leave the animus.
- "Disciple of the Creed": This one should come naturally for most completionists. Just make sure that you complete all investigations, highpoints, and save citizen missions in the district BEFORE you carry out your assassination.
- "Blade in the Crowd": This only has to be done on one target, and most people get it on their first. If you miss this on your first target don’t worry, there are at least three other opportunities.
Step 2 – Masyaf – 4 
The game starts with a very linear introduction where you learn the controls and the basic premise of the game. There are three storyline achievements right off the bat, then you will be able to explore the city of Masyaf. Get the flags here using http://www.assassinscreed-maps.com/ for your 4th achievement.
Step 3 – Linear progression – 20 
Note: Absolute Symbiosis is not technically a linear achievement, but completing each district in a linear fashion will net you that achievement as well.
Step 4 – The Kingdom - 3 
If you are using http://www.assassinscreed-maps.com/ the kingdom is a breeze. Just go to each city, ticking off the kingdom flags that you get along the way. At some point, come through and get all the remaining flags, templars, and high points. If you aren’t using this site, I would recommend not getting any flags at all in the kingdom until you’re ready to do a flag hunting marathon. In addition to the Kingdom Flags achievement, this should complete your kill all templars achievement, and reach all high points.
Step 5 – Performance achievements – 13 
These are achievements like perform 50 combo kills, or assassinate 100 guards. Most of these will come naturally if you just don’t run and hide much. What I did to ensure that I got these quickly was to try to only kill guards using one method at a time, eg. I only assassinated them, then when I got that achievement, I only used combo kills, etc… The only one that might give you trouble is pickpocket 200(!) throwing knives, since you can only grab 5 at a time. Also, there’s no need to boost Eagle’s dance. If you just leap off every highpoint, you’ll get it eventually.
Note: See "Eagle’s Will" for a reliable glitch.
That should be 1000/1000. If you’re missing a flag, just go to http://www.assassinscreed-maps.com/ , clear all the flags in the area that you’re missing and and go through each flag location. Same with templars. Everything else should be apparent.
[XBA would like to thank IWi11KickU for this Roadmap]
"The DNA bar is the bar that fills up as you complete the investigation missions in each memory block. In order to get this achievement, simply complete all six investigations for each assassination rather then stop after three."
"Again, this achievement really only requires awareness and patience. You need to assassinate every target with a full DNA (health) bar, not just kill them in open combat. Make sure every assassination is a one-hit kill with your hidden blade. This doesn't mean that every assassination must be a low-profile hidden-blade attack though. Holding down for a hidden-blade strike for a high-profile assassination will still score this achievement."
This achievement is currently glitchy. It has been confirmed that the above will get you the achievement, but less also will. Also, if you have every side mission done before you start the assassinations, it will unlock. For updates, check this -thread-
As it says you must defeat 100 opponents without dying.
Spend the majority of your time blocking.
Always try and counter kill them as it is a lot easier.
Run around the city killing every guard you see.
If you are having trouble, this glitch works for some reason:
At the start of the game in Masyaf, run along the far left side of the village until you see a spiked outcrop pointing up toward the mountain with a tree just in front. If you run into the corner at the point while moving left and right, you'll be able to wriggle up the cliff face. When you reach the top, jump off the edge of the map and you'll unlock the achievement!
Credit goes to Mullock94 for the method and Moonska for the video.
A single fight means that your synchronization bar must remain red throughout the entire fight.
Attack a guard and hold block. Keep backing away around the town and gather a group of guards. The max I could get at once was 13. Once you've gathered the maximum (again 13 for me), kill them until one remains. Then gather another group and kill that twelve. I find it's safer to gather a third group and then kill them all. This makes sure you actually got 25 instead of 24.
The first mission that your leader sends you on. Just gather information and find the traitor in Masyaf
For additional help with the Templars and flags, try this -thread-
For additional help with any part of the story, try this -thread-
For the Eagle achievements, the score is specific to the game save, so getting 25 leaps of faith in one save and 25 in another will not unlock the achievement. All 50 must be done in the same game save file.
When killing Robert de Sable, watch out for a glitch by the two archers that may cause you to fall into the floor. If you've fallen foul to this you will need to take your HDD to a mate's house and complete it there. Or it has been suggested to use a Lens cleaning Device.
Red dots are the flags. The numbers correspond with a location guide found HERE