A very simple and absolutely legal question. Unfortunately it has no simple answer. This is one of the biggest oddities for many VaM users.
This is how I would do it: copy your complete VaM installation folder to a external/spare drive for safety reasons. Now install VaM and copy/move everything you want to keep to the appropriate folders.
Your own presets, looks and scenes are saved locally. The best way to find them is to look at the file browser menu for the correct local path. Some are in VaM/saves/ other are in VaM/custom/atom/person/ folders and so on (I am at work and can't have a look).
So far so good... The big problem is, those scenes and looks all have dependencies to other stuff and plugins and nowerdays most of them are downloaded ".Var" files hiding in the big mess of the addonPackages folder. You almost can't delete stuff without breaking your own custom creations.
Unfortunately there is currently AFAIK no tool to help you with this!
This is a true pain in the ass and a lot of work for people with lots of custom stuff. I pray to the plugin coder gods to give us an (un)install manager.
If you have your own looks, presets or scenes, you have to copy them over, try every single of them and take a look at the error messages. For downloaded stuff I literally would abadon everything and download your favorites again with all the displayed dependencies.
My personal methode is the quick and dirty way and not very effective. I look through my install folder and delete only the biggest bummers. I am very curious about other users answer on this question.
Edit: Never have done this myself... In theory you have the option to create your own .Var files for your own custom stuff with the package creator. This will automatically add local dependencies and put out a list of all used .Var files. Though, this is quite cumbersome and if you have tons of older local stuff (not in .Var files) like clothes or morphs, this will multiply the needed disk space.
Edit2: For your own custom looks there is a plugin called MorphMerger to bake all used morphs together to only a single one. The downside of this is, you can't edit those looks by changing the used morph values anymore.