Every person, pet, food, drink, tools, water hose, sewer hose, LP, water, tv, dishes, silverware,paper plates. Think what you have in your house that you use on a daily basis, that you might use while camping or traveling. Any and all options that have been installed on your trailer. (awning)?
Anything you will be adding/putting in the trailer or truck will all count.
As far as weighing, is there a truck stop close to you that has a scale? Other wise some of the feed mills also have scales. Ask around locally. You might be surprised what there is available in your area that has a scale.
If you do find a place to weigh, try to do it with everything loaded like you would have it for heading out camping/traveling.
2008 Cruiser CF26RK
2013 Ford Eco-Boost
Heavy duty payload - Max tow