Any info needed from ISP?

I am quickly approaching the installation of Asterisk for my business. I was curious if there was any information I should get from my ISP/phone provider before setting the system up. I am sorry if I missed this in any of the articles.

I love the vast amount of information on the site and most of all the forums. Great work by everyone that has contributed. I look forward to participating in future discussion.

All the information needed to configure a SIP peer.

Typically: the address to use for outgoing calls; any differing addresses from which incoming calls can arrive; how they expect caller ID to be passed; how do they vet caller ID; do they require a particular value in the user field; do they insist on their domain, rather than yours, in the domain field; what codecs do they support; do they support re-invites; etc.

Generally a good ITSP will have standard parameters for Asterisk. Unfortunately they are often based on an obsolete version and take the view that it is better to work first time than be secure.