Welcome, MTF!
My best advice for setting up your categories, espeically in your lists, is to keep it simple at first and then branch out from there. I at first got so excited that, in addition to the basic @waitingfor, @home, @internet, etc, I also added a whole bunch of other "creative" lists that it turned out I always forgot to look at. But do customize to your own needs. For example, the way I work, it just doesn't make sense to have separate @phone, @computer and @work lists -- they are all lumped into @work.
I think most people on here have each next action as an item on a todolist. That item also has a note attached (in which you can store whatever data you want about that item), and has a category. The categories become the identifier of which list the item is on. You can sort the items by category to view any one of your different lists (or all list items together). It is also easy to switch a next action from something you need to do "Call Sally re movie time" to a @waiting for item by just changing the category to @waiting for, you don't even need to change the title of the action.
Another idea you may want to consider is for project based next actions, somehow inserting the project name in the title of the list item. For example: "XMAS PARTY: make list of guests". This is useful for a couple reasons. As you will shortly find out, Palm won't let you assign two different categories to a project. The result is that you can't sort by project without extra software. So you can't click a button and have your palm show you all the things going on for the xmas party (make list of guests, internet research re recipe, waiting for harpist to call back, etc). But, having put "XMAS PARTY" in the header for every action related to that project, you can hit your little "search" icon, type in XMAS PARTY, and they will all show up in your search window. I use all caps for the project name, then regular font for the NA for that project. There can be many NAs for a particular project, and they all bounce around between the different lists independently, but they all have the project name in the title. I think others on this forum do something of the sort also. This has been my best productivity enhancer. It is good for instant retreival too - if my boss walks in and says "What's the status of Client X's transaction?" I just type in Client X in the search window and can go quickly to the todo items related to him without having to scan through the different lists manually. This made a big impact recently at a department meeting - one of the partners said "Wow, how did all that information get IN there?"
I'm going to start another post re memos categories asking people to tell what their categories and interesting memos are, I think there will be alot of creative things popping up.
Again, welcome, and enjoy using GTD on your palm!