Source. And a source for non-journalled quotas. 

aptitude install quota

Edit fstab to make the proper entry look like this: 

/dev/sda2       /               ext3    errors=remount-ro,usrjquota=aquota.user,grpjquota=aquota.group,jqfmt=vfsv0 0       1

I don’t know if errors=remount-ro is a default option that will be enabled anyway. I would guess so.

Do this: 

touch /aquota.user /aquota.group
chmod 600 /aquota.*
mount -o remount /

Then: 

quotacheck -avugm
quotaon -avug

WIth this command, you can set a 1GB quota for a user: 

setquota -u $user 0 1000000 0 0  /

Other tools of interest: edquota, repquota. See the seealso for any quata command, I guess.