Jerry, you're going to confuse the newbs.
If you don't know the person who offered the trade, use extreme caution and unless they're someone well known with a good reputation, like Jerry, DO NOT ship first.
If you offer the trade, even if it's to an unknown person with no reputation, you ship first since you offered. Again, be very sure who you are shipping to. If the deal sounds too good to be true, it probably is, take a pass. There will ALWAYS be another snake you like out there waiting for you to find it.
Caution is the key word. Use the BOI on Fauna and ask on any site that pertains to whatever species you're trading.