I started by setting up some "Generic Gestures" as I called them. These gestures for for land, water, big, small, etc. Some things that would be used over and over again and would need to have the same gesture.
Land- I pat the ground 3 times (standing of course just move hands up and down 3x with palms facing the ground.)
Water. I use my hand to go from right to left in a "wavy" motion.
Small- I pinch min fingers about an inch apart
Big- I do the "Y" in the YMCA dance.
The rest is made up of kid ispired gestures of what I came up with. The most fun part of vocab day forme with gestures is when we do our formative assesement and I use the gestures and they have to write what I am describing. When I get good at this I would like to have the kids read a passage and then I would explain using only gestures, a kind of "Geography Sign Language" I was able to do this with my advanced class of US History. It was pretty amazing.
Back to gestures. Here is an example-Harbor- our text has it as "A sheltered area of water deep eough for ships" So I made the water gesture, then brought my arms together in a 3/4 circle then placed my hands palm togther and dropped my bottom hand as our symbol for "deep" (the opposite is used for mountains for elevation) and made a motion like I was driving a ship on the old wodden wheels. Then for Bay which is the same defination but not deep enough for ships we made an X with our arms and made the rest of the gesture as to say "not deep enough for ships"
Ive done many with US History covering ideas like, renaissance, Islam, Muslim, Crusades, Reformaiton etc. To me those are easier than the land forms.