Just a few asterisk commands:

reload soft-restarts Asterisk and updates internal configs with changes you’ve made to /etc/asterisk/* - does not hang up calls
sip no debug Disable SIP debugging
show dialplan shows the full dialplan of how your calls will be handled
sip show peers shows all registered SIP clients
sip show channels shows current “live” channels that are in use by SIP clients (off-hook)
sip show registry this command will show you the status of any SIP connections with remote hosts. (eg: Your VOIP carrier.) If you have an authenticated connection with them, it will show as registered otherwise it will show it as unregistered.
sip show users this command will show you a list of all the SIP Users setup in the sip.conf - along with their secret password. This is great for when you go to setup the phones.
database show database Dump
sip debug ip Enable SIP debugging on IP
sip debug peer Enable SIP debugging on Peername
sip no debug Disable SIP debugging
stop gracefully shuts down Asterisk after all calls have hung up
stop now shuts down Asterisk, hanging up any current calls