Multiple-choice field in Business process flow

Hi,

I know that there is a way to add  N:N relationship, and it will show as sub-grid.
But this is only possible to add to form not to business process flow or quick create form.

So my question is, what is the recommended/best practice way, or way you use when u have multiple choice field, that u should put in business process flow or quick create form?

Thanks for sharing your opinions...