Assassin's Creed 3 Achievements - Guide

An Extraordinary Man
Complete the Encyclopedia of the Common Man

Complete the Homestead missions to get workers at the Homestead. Then, with the mission from Achilles, interview everyone.
Patent Not Pending
Craft one of Franklin's inventions to decorate your Manor

House Party
Recruit any of the Artisans and see them settled on the Homestead

You will unlock this as soon as you recruit one skilled person for your Homestead. Complete Homestead missions for this.
A Complete Set
See all the optional characters settled at the Homestead

Complete all the Homestead missions to get everyone to your Homestead.
Original Gamer
Win a game of Fanorona, Morris and Bowls on the Homestead

Find and play the games.
Bring Down the House
Explore Fort Wolcott
Kidd Gloves
Uncover the mystery of Oak Island
All Washed Up
Complete all Naval Missions aboard the Aquila
Entrepreneur, not Pirate!
Complete all 12 Privateer Contracts
Upgrade the Aquila

Buy the rather expensive upgrades for your Ship from a Harbormaster.
By Invitation Only
Be invited to join a Club

You should get this quite easily from hunting or any other side quests.
In Good Standing
Complete all challenges for any of the Clubs

Follow and complete all the tasks the club gives you (you can find them in your menu under Logbook).
Man of the People
Liberate all districts in Boston OR New York

Fight the Templars from each zone of either of the two main cities.
Monopoly Man
Send a convoy to Boston, New York and the Frontier

From your Accounting Book, send a convoy of materials or products to each of the three areas.
Blowing in the Wind
Retrieve every page for one of Ben Franklin's Almanacs

See: Blowing in the wind Achievement
Complete ALL progress tracker grid entries
Complete 50% of the Progress Tracker entries
Spit Roast
Perform a double assassination using a musket

Pick up a musket, assassinate a soldier while one stands behind. If loaded, it will fire once you stab one, killing the second.s Video here:
Circus Act
Kill 15 guards with a single cannon shot

During Sequence 10 you have a cannon in the last mission. Video:
Hang 5 enemies by using rope darts

Easy in the Frontier. Video:
Prince of Thieves
Loot a convoy without killing any of its guards
Whit's fur ye'll no go by ye!
Block a firing line 5 times by using a human shield

You are shown how to do this during the mission. Grab a soldier to use as a meat shield while a firing line is about to shoot.
Jager Bomb
After becoming fully Notorious, kill 10 Jagers before losing your notoriety
Magna cum Laude
Have a Trainee reach the Assassin Rank
Coureur des Bois
Exchange undamaged pelts at all different general stores
Eye Witness
Witness a predator killing an enemy

You can easily witness this whilst hunting, especially in zones with Bears and Bobcats.

Mission Achievements

Rude Awakening
Re-Enter the Animus
No Good Deed Goes Unpunished
Open the Temple Door and learn Desmond's fate
Mystery Guest
Complete Sequence 1 & 2
How D'ya Like Them Apples
Complete Sequence 3
Heroes are Born
Complete Sequence 4
The Day the Templars Cried
Complete Sequence 5
Tea is for Englishmen
Complete Sequence 6
The Whites of Their Eyes
Complete Sequence 7
Caged Wolf
Complete Sequence 8
Two if by Sea
Complete Sequence 9
Grim Expectations
Complete Sequence 10
Difficult End
Complete Sequence 11
The Sum of Truth
Complete Sequence 12
Complete 100% of all main mission constraints
Complete each of the epilogue missions unlocked after the credits roll

Secret Achievements

Daddy Dearest
Complete Present - Stadium
Criss Cross
Complete Present - Skyscraper
The End is Nigh
Complete Present - Abstergo
Head in the Cloud
Find all pivots and sync the Animus to the Cloud

Multiplayer Achievements

Abstergo Entertainment
Reach level 20 in the multiplayer mode
Reach sequence 10 in a map on Wolfpack multiplayer mode
Winning Team
Be on the winning team at the end of a multiplayer game session
Customize your multiplayer Profile and Character
The Truth Will Out
Unlock a hacked version of one of the Abstergo videos in the story quest