Don,
ASGCA has a standard "Request for Proposal" form available that many clients use. There are many blanks to fill in, so you can customize it to your particular needs.
You can send it to the entire ASGCA and NGF list of architects, or pick and choose up to a dozen that make sense to you, either by reputation or geography. Unlike local construction projects
The RFP document also follows the best process, saying you will get in information from all interested respondents, narrow the list to three to five to interview, and make a selection and negotiate fees and services.
You can order the document from asgca.org, or call them at 312.372.7090. call me if you want more help!