A shared application, especially, should always be split. Only the back-end
(the tables and relationships) should be on the server: each user should
have his/her own copy of the front-end (the queries, forms, reports, macros
and modules), ideally on his/her hard drive.
While reading the sites suggested by other respondents, keep in mind that
this isn't an "it would be nice and slick to do it the way the MVPs do"
issue, its a "this is how Access was designed to be used and you'll have
lots of problems with a shared app if you don't" issue.