Trivial newbie problems with LUKS encryption

Hi /r/linuxadmin,

Perhaps you can shed some light on these, please:

1. I have to modprobe dm_crypt after every reboot. How do I configure it to happen by itself?
2. LVM encryption confuses me a little. on /etc/crypttab, what's the correct format to add the device to be mounted? There are a few options:

/dev/sdc1 - partition name

/dev/mapper/secure-logicalvol - the name of the LVM

/dev/hannahs-volumegrp/secure-logicalvol - uh, this full path format thingy

uuid=1234-abcd-etc etc.

All of the above perhaps? Doesn't seem to do the trick. Possibly related to the kernel module probing issues.

Thanks!