Wow...just ran across this
Firestone "How To Weigh Your RV or Trailer" that gives you a form and step-by-step instructions on how to
properly weigh your rig.
I found it via a link elsewhere that goes to a fantastic site,
RV Towing Tips that has a world of simple info if you are new to the world of RV'ing (and some for those who AREN'T!

). It not only covers the "Hot to Tow" part, but many other aspects such as buying tips, brake controllers, Towing Laws, hitches, and many others. I've seen quite a few websites that try to be comprehensive, but so far this one takes the cake.
I find this so outstanding that I'm going to make it a sticky for some time to come- let us know what you think, and what you've learned!