Entering data into 2 tables by 1 form

[The Last Day]

Is there anything to keep in mind when I build a form that I intend to use to enter data into two tables?

 

[MarkK]

This rarely makes sense. If your user interface groups particular data together on the same form, why are these data not in the same table?
More typically, related records have a One-To-Many relationship, which is very difficult to represent on a single form. It is far simpler to represent the One side of the relationship on the main form, and use a subform for the Many related records.