Hi. I'm new to using the Creation Kit, so some of what I'm about to say is probably obvious to many of you. I ask that you please be patient with me. I've noticed that for all of the NPC's that become your followers, as well as NPC's that are converted to followers via mod or console command, the following menu options open up for them:
1. Wait here / Follow me
2. I need you to do something
3. I need to trade some things with you
4. It's time for us to part ways
This indicates to me that when an NPC is made a member of the follower faction they acquire an AI package which includes the above dialog options. It also occured to me that if you wanted to add a command for an NPC, say "Sit here", then you could just edit the associated AI package. But as of yet I've been unable to locate this AI package, or the spoken dialogs for these options. Any help that you can offer would be greatly appreciated. Thanks in advance.

For this you need to create AI Packages. Do you know how to create that?

The quest DialogueFollower has the dialog options for vanilla followers.

To get those options, I believe all you have to do is create your follower and add the factions:
-1 Current Follower
0 Potential Follower

Just doing that has made my newly created NPC follower have all those dialogue options. Now we just need a Dark Faces bug fix.