The meetings are usually in the form of conference calls. Regular email correspondence is commonplace for both status updates and information requests. The only regular meetings we have are in the beginning to assure you understand the document and actionable needs (which we offer up in an organized and prioritized list), and a final meeting to go over the fine-tuning before your offer is submitted to the GSA.
The GSA is going to perform a competitive analysis, which sometimes is not apples-to-apples, and they will likely recommend your prices come down. We usually perform a similar analysis, and submit this with the offer to assure the GSA understands the fairness of your prices from the beginning. Also, we equip our customers to negotiate with the GSA. This includes how to ask follow-up questions, terminology, and which counter-offer options are available to you.
For most GSA Schedules there are little or no environmental requirements. However, if your products are certified in any way, make sure to mention it in the product description, as many Federal Agencies are actively rolling-out internal sustainability goals. So, if all other things are equal, green points can make the difference in winning a bid.