Define models in Django
To do this, I would recommend breaking down each individual relationship. Your relationships seem to be:

Authoring
Following

For authoring, the details are:

Each Question is authored by one User
Each User can author many questions

As such, this is a One-to-Many relationship between the two. The best way to do this is a foreign key from the Question to the User, since there can only be one author.
For following, the details are:

Each Question can have many following Users
Each User can be following many Questions

As such, this is a Many-to-Many relationship. The Many-to-Many field in Django is a perfect candidate for this. Django will let you use a field through another model, but in this case this is not needed, as you have no other information associated with the fact that a user is following a question (e.g. a personal score/ranking).
With both of these relationships, Django will create lists of related items for you, so you do not have to worry about that. You may need to define a related_name for this field, as there are multiple users associated with a question, and by default django would make the related set for both named user_set.
I'm new to Django and I'm trying to create a simple app!
I basically want to create something like StackOverflow, I have many User and many Question. I don't know how I should define the relationship between these two Models. 
My Requirements:

I want each Question to have a single author User, and a list of User that followed the Question.
I want each User to have a list of posted Question and a list of followed Question.

I'm pretty much lost, and I don't know how to define my relationship. Is this a many-to-many relationship? If so, how do I have like 2 lists of Question in my User model (Posted/Followed)?
Please help!