Best practises for Configuration Management before build

Hi,

As there are many experts in Configuration Management in this group I ask of this opinion here -
Before doing a build there may be a practice to check all working copies if there are any files which are modified but not checked-in.
So one person may go around checking status of files in each person's working copy and accordingly check-in files which are not checked-in.
Is there any other way to ensure that developers have not inadvertently left out checking-in files which they should have checked-in?

Regards,
Rupa