[AccessD] design/development question on representing mtm relationships

During a training session yesterday I had someone ask me what the easiest
and best way to represent a many-to-many relationship for data entry. I
admit, I was a little stumped and replied that the form/subform was probably
still the standard solution but he's got me wondering -- how does everyone
else handle it? I can't see any reason to really defer from the
form/subform, but now I'm curious what creative solutions others might use. 
 
The other question I have -- and this one's my own -- I know there are a few
easy ways to handle new primary key values when entering the many side of
the relationship first -- pop up forms probably being the most common and
even combo box controls that allow new values -- what do you guys do? Do any
of you force the users to enter the one side first, which often seems a bit
unnatural to the data entry operator? 
 
These aren't really technical questions, so much as they are just
design/solution type questions. I'm interested in hearing what other people
do. 
 
Susan H.