This has been patched so if you are going to start the game now make sure you download the patch and just skip to the action list.
You must do all the homestead missions in order to unlock every worker. After you have done that, go to the homestead and each of them will be doing something different. From there point your cursor at them and hold LT and it will let you know if you recorded the action or if it is invalid.
If they are doing something that you have already recorded, simply use fast travel and come back.
Another note is that they DO NOT come out at night. You can either wait for daylight or finish the game which grants you the Animus weather hack where you can change the day.
EDIT: From what Pinkie Pie 91 and Mr Stoat are saying is that there are many more actions than the ones I listed so you do not NEED to see these specific actions i listed. Meaning when you go and check on the people, if they are doing something different then scan it!
EDIT 2: Press START and go under the ANIMUS DATABASE and go under ITEMS and click Encyclopedia. Everyone that is listed on there, you already have recorded. Wife of one of the lumbers' churns butter.
EDIT 3: Ubisoft is releasing a HUGE patch next week and here are the fixes they will attend to INCLUDING this achievementhttp://kotaku.com/5961200/massive-assassins-creed-iii-patch-...
Also if you wish to wait until end game you can obtain the animus hack "Sun and Moon". This will keep it daytime permanently and it will not AFFECT your save progress or achievements.
UPDATE 2: Good news everyone! I found a way to get the achievement without it glitching out! The bad news is you have to start the game over.
So what I did was the homestead missions as they came out but here's the catch. You should scan an artisan right when you get them.
Here's the order in which they came in
The first three after the huntress are incredibly important! After completing the huntress, you should complete the woodworker before you start anyone else. Then simply move to the lumberers,
The best part about the first four is that you do NOT need to do any of their missions in order to unlock more actions as they have 3 base actions to start with. Complete them and continue the story until the homestead mission for the farmers show up in the frontier.
Also I didn't record the lumberer's wife churning the butter so you might want to avoid that to be safe.
After every mission check the frontier for the farmers to show up. Right when you get the farmers, go back to the homestead and SCAN them until it is complete. Do not wait or their homestead missions might show up and it might glitch out.
After you scan the farmers, woodworker, lumberers, and huntress. You are basically home free because from there the miner, doctor, innkeeper, tailor, and blacksmith does not glitch out. But to be safe as soon as you get another artisan try scanning them and complete them as soon as you can.
To make it day time, simply start a naval mission and exit out of the memory.
Some people have their woodworker 2/3 but instead they needed to get the lumbers scanned to complete it.
The other problem is the farmers that are 3/3 even after scanning every available action, there is no completed entry and that's probably the glitch that no one can seem to figure out and I haven't found a solution..
This is the full list
(credit Morbious17 for the actions)
Tailor- Across the blacksmith, bottom south west house of the map ( El )
Measuring dress shirt
Sewing in chair
Checking out the chair
Innkeeper- North of tailor's house ( Ol & Co )
Rotating food on spit
Watching livestock grind wheat
Doctor- west of lumbers, north of innkeeper ( Ly )
Tending to herbs behind his house
Reading a book under a tree in front of his house
Playing a game of Bowls
Tending to man in chair
Blacksmith-Bottom south east house, across tailor's house ( Da )
Nailing shoes on horse
Constructing wagon wheel
Miner- West of the bottom river, his mine is directly south of his house ( No )
Lighting lantern at mine entrance
Getting pickaxe from shed/mining with pickaxe (considered one task)
Sifting by the river
Farmer- southwest from the manor ( Pr & Wa )
tending the vegetable garden
watering the garden
collecting honey from the bee farm
Lumberers South of the manor, Can't miss it ( Te & Jo )
Putting wood in wagon
Using two-man saw
Huntress- Lone house, North of the top river ( My )
Rotating food on spit
Firing musket at an animal
Firing the musket at game
Skinning the deer hanging at her camp
Woodworker- Across innkeepers and south of lumberers ( La )
Cleaning a chair
Sanding a piece of wood
Examining wheel barrow contents while writing in a book
Checking the fence
Thanks to all the great comments which have different scenarios/locations.