I use 2 large, low profile containers (one for electrical stuff and one for water stuff), a Home Depot bucket with a lid to contain the sewer stuff, and a tool bag for the tools. Those go against the front wall. The grill (fold flat Roadmate), chairs, and WD/trailer jack parts I just put in there against the back wall. All has to be loaded from the passenger side because I have a built-in generator on the driver's side. I like the containers because they are easy to grab and slide. I use a rubber mallet to reach for the back stuff (don't judge!), but I sure do like the idea of eye bolts on the containers for easy grabbing.
Stuff like wheel chocks and levelling blocks go in the truck bed.