BioShock 2 Remastered

Overall there are six Little Sisters in Minerva's Den, in two sets of three. A Big Sister also attacks you after each complete set.
YOU DO NOT HAVE TO SAVE THEM OR PERFORM GATHERS TO GET THE ACHIEVEMENT.

Little Sister One:
In the Lobby of the Corporate Offices, on the rare occassion you may have to wait for the Big Daddy to get the sister out of a vent first.
Gather 1:
Near the Gene Bank in the lobby, best way to survive this is to use Ion Cannon and Security Command.
Gather 2:
Inside the Robotics Showroom, after scouring for the collectibles in the room, go back to the corpse near the water. Hack the security camera for added protection and use Hypnotize on the Spider Splicers. Try to get them to set the alarms off for Bot support.

Little Sister Two:
Inside Robotics Workshops. Cross the beam and get Elctro bolt from the room the other side. This triggers the Little Sisters to come inside the room below. Hit the Lancer with a security command and a couple of heat seeking rockets, then retreat and hopefully the bots should finish him off for you.
Gather 1:
This can get you Master Gatherer from the main game.
Get lots of first aid kits just incase you do screw up, then put the little sister down on the corpse in the room you just adopted her in. Then go back to the beam you crossed before, ring the little sister with trap bolts. Now the first splicer to enter the room, you should use hypnotise on before they spot you, repeat this everytime they die. Hopefully, this will mean you won't need your trap bolts.
Gather 2:
Up the stairs in system design of McClendon Robotics.
Hack the camera in the corner by the safe you find in the room. Set up trap rivets around the corpse in a ring and make sure you save your miniturrets. Place two nearby the corpse but outside of the ring.
Thermal cells are your best weapon, hypnotize the most useful plasmid.

Little Sister Three:
On the way out of the warehouse around Air-Tite Archives. Lure the big daddy downstairs and if you hacked the rocket turrett downstairs this helps a long way. It's a similar tactic to before.
Gather 1:
Where the rocket turrett is, there is a corpse by the stairs to the right.
Use trap rivets and use hypnotize on splicers.
Gather 2:
In the reception area of Air-Tite Archives.

A Big Sister battle will take place before the gathers if Little Sister 3. From here, I won't be making notes on how to perform the gathers, simply as you should now have all the achievements for them.

Little Sister Four:
Early in to the Operations level, you'll come across the little girl inside the lobby on the way to programming.
Gather 1:
Close to where you pick up the sister, near the Gatherer's Garden, up the stairs.
Gather 2:
System programming, north of Whal's Office in the main room.

Little Sister Five:
Outside the main room at Wahl's Office as you exit with the signal beacon.
Gather 1:
Data Processing, in the server room below the locked room with all the ammo and extra goodies
Gather 2:
System Programming, where you find the Handy Machines tonic.

Little Sister Six:
You may have to wait for the Big Daddy to go to a vent to get her out. Then wait some more until they're far enough away that you don't scare her back in the vent.
On my playthrougg, by the time I did the objective, the big daddy had already got the Little Sister and started moving around. Anyway, she's outside of Turbine Control in the Climate Control area.
Gather 1:
Turbine Control, not far from where you adopted her. This is a really hard gather, so if you're still tidying up achievements, don't attempt it here.
Gather 2:
In the room with the large tank in the centre, where your final Vaccuum bots happend to be.

Big Sister fight will seperate Six and her gathers.