Getting an Autonomous System Number
Get the ASN Template from ARIN and fill out sections 0 through 3. Line 0 should be "N". Line 1 is just a short version of your company name; it can be up to 21 characters. Section 2 is your company information. Section 3 is the info for the bgp-knowledgable person in your company.
The justification goes in section B and describes your need for an ASN. State that you will be peering via BGP4 with Citynet (and your other upstream providers). List the IP prefixes that you intend to announce. ARIN can contact firstname.lastname@example.org to verify that you have connectivity to the Citynet network. You will need to provide similar contacts at your other upstreams as well.
Send the completed form to email@example.com . You should receive an automated reply within an hour and a human reply with 1 business day. They may ask additional questions of you or your upstream providers. It is very important that you respond to these questions in a timely manner. After ARIN agrees that you have valid need of an ASN you will need to fill out some billing information on this template. There is a one-time fee of $500US for an ASN to be assigned. After one year, there is a $30US maintenance fee.