I'm trying to allow the user on my website to subscribe to a specific newsletter of their choice. Problem is that currently you must choose a newsletter to generate a subscribe form and only then you can choose to select other lists.
How do I let the user choose which list to subscribe to?
There are a couple ways you can have 1 form to subscribe to multiple lists. First, you can have 1 list and use segments to create multiple "lists". Basically you'd have a field for list and options for each section and segment based on that. Then the subscriber make their selection and they're placed on the segment of their choice. The benefit to that is not only can you create segments and send separately to them but you can also give them the option of modifying their list preferences via the preference center later.
Second, you can use the multiple list options via the form. But create 1 "main" list which is never used and use that for your form and then add in the option for all your other lists. Anyone subscribing is always added to that main list (which you wouldn't send to, it's just there to create the form basically) but then has the option of selecting their lists. All they know about are those list options. In this case you will have separate lists as well, but they wouldn't be able to modify their list options via the preference center then.