To use the short syntax, ie "mount /mnt/hda1", you must have a entry in /etc/fstab for the partition.
/dev/<partition> <mount point> <filesystem type> <mount options> <dump> <fsck>
You can use something like this for a vfat partition
/dev/hda1 /mnt/hda1 vfat noauto,uid=500,gid=500,umask=007 0 0
The mount options you use are dependent on your needs. Look at the manpage for mount for the options available for specific file systems.