Before any of my clients makes an offer I run a CMA to come to our own assessment of a fair price. I use that information when presenting the offer, in person whenever possible, so the seller has a clear understanding of the basis for that offer. This is valuable in all transactions, but may be even more so in offers to FSBO property.
My goal is to present a fair and well thought out offer from the start. This places the buyer in a strong position and improves the prospects of obtaining the desired property for the best possible price with the least amount of negotiation delay.