Here is how I do it:
I have a file ~/.smb/creds:
The mount command is:
smbmount //computer/share /path/dir -o credentials=/home/user/.smb/creds
Problem with using fstab is that the network is not up by the time it is processed.
I call my mount command from KDE's Autostart folder.
You can also use /etc/rc.d/rc.local, but that one is run as root, which may cause some read-write issues.
Here is a guide on using ~/.bashrc: http://blog.unixlore.net/2006/05/accessing-windows-shares-from-gnulinux.html