How do I change the /tmp location?

I’ve got a box running RedHat 7.2 and Samba. Things work beautifully with one exception:

When a user goes to copy files to the Samba share the files firt hit the /tmp area, which only has about 300MB free drive space. The user’s file size is bigger than that so the copy fails. Does anyone know how I can get Linux to use a different area for the temp files?

I’m trying to point them to /home/tmp which is on a much bigger partition, but I couldn’t seem to make Linux cooperate.