Have you ever wondered why the heck you write jls then jexec JID /bin/csh?
I got sick of this few year ago and I wrote a tiny little script that makes my life easy every day.
Be warned, there are few cases when you'll have to see your jid but this works with jid too.
(for example when you have hang jail that won't shutdown /stop/ - happens to me pretty often and this is reported as non-critical bug for years...)

How it works?
Let's pretend that we have a jail named: 'mailserver.valqk.com'. Then you simply type this to get in the mailserver:

#>jlog mail
Logging in to mailserver.valqk.com
mailserver#                           

It's that easy. Also you can add a preffered custom shell for this session after the jail (or part) name.

What looks like the script itself?
There it goes:

#!/bin/sh
[ -z "$1" ] && echo "No jail specified." && exit 1;
[ -z "$2" ] && loginSHELL="/bin/tcsh" || loginSHELL="$2"
jName=$1;
jID=`jls | grep $jName|awk '{print $1}'`
jRealName=`jls | grep $jName|awk '{print $3}'`
[ -z "$jID" ] && echo "No such jail name $jName!" && exit 1;
echo "Logging in to $jRealName"
jexec $jID $loginSHELL

please feel free to use, comment, improve this script! If you make any improvements, pls tell me!
I'll definitely add changes if I like them!!!