The April 6 and May 4 caucuses are for selecting the delegates to the national convention in Denver. Obviously this happens only once every four years. You've probably read my essay on that procedure, but I'll kick it to the top to remind everyone that the time to submit paperwork is drawing near.
The state convention is held every year in June. You should contact your county party chair about becoming a delegate to the state convention. You could also be a delegate to your congressional district convention, or at least a guest, if you act quickly, because your 3rd CD convention is this Saturday, March 29, in Sparta. Every congressional district holds a convention during the spring (one purpose of these is to pass resolutions that are sent on to the state convention). Delegates to the CD conventions automatically become delegates to the state convention also. Here's a link to information about the CD and state conventions:
http://www.wisdems.org/ht/d/sp/i/1015605/pid/1015605(And a note to 5th CD members: the CD convention call to order is at 1 pm, not 2 pm as on the website. :( )
This procedure truly is complicated, but just ask and somebody will be glad to fill you in. It's going to be an exciting year!