If you want to define the umask for a specific directory (example: group write permissions for a directory you use together with your colleges), you'll become sweating when using the umask command because it is always valid for all directories.
The solution of this problem is setting a default ACL. The following command ensures that all new files in /home/shared/ have all permissions (including write permissions) set for the group:
setfacl -d -m mask:007 /home/shared/
You should also set the sgid-bit for the directory and choose the wanted group using chgrp:
chgrp the_team /home/shared/
chmod g+s /home/shared/
If /home/shared/ already contains subdirectories, you have to change their permissions as well. Tip: all mentioned commands know the -R option.