Rules of thumb...sell nothing but the need for an appointment on a phone call or initial call.
Also never "sell" during your fact-finding for several reasons:
1.) The fact-finding process gets interrupted or stopped.
2.) You come across like a dog salivating over fresh meat.
3.) You tip your hand and lose some of the thunder you will get from your proposal.
4.) You inspire additional questions and thought processes that the prospect will then discuss with competitors.
5.) You may be "selling" based on the wrong conclusion. Try to resist making proposal decisions until the fact-finding is over and you have had a chance to think things through.
6.) Oftentimes, the perceived need is only a small part of a much larger problem that may only become clear (to you and the prospect) after complete fact-finding.