Configuring the temporary directory
Check  Administrator -> Configuration -> Media -> File System to personalize your tmp path. Make sure to use relative paths and have the right privileges for the Apache user.

I personally like this article fix file upload. He has good observations. It worked for me.

Recently, I downloaded my site to my Mac computer. It happens that in my Mac I was using mod_userdir for Apache and I forgot that in /etc/apache2/users/nameofuser.conf I need to set AllowOverride All, otherwise I will have the following message:


  The specified file temporary could not be copied because the destination directory is not properly configured.