Hello, and welcome to LinuxQuestions.
Well, it all depends on where you want to mount it, right?
I prefer /usr/local/storage for added disks that aren't used for the system itself (only data storage with mp3's and stuff like that). You say you can mount it manually so I guess you have your mountpoint set up as you wish already.
A line in /etc/fstab to mount an ext3fs-formatted partition could look something like this:
/dev/hdb1 /usr/local/storage ext3 noauto,noatime 0 0
The "noauto,noatime" is only my preference, you could use "defaults" instead.