Not sure there are any ( at least I don't know of any). Some rules of thumb (also do a search for metaballs on forum). 1. Treat them as virtual clay. 2. The object box dictates it's influence on other metaballs (the closer the boxes are to each other the more they melt together) 3. Grouped metaballs don't interact with other metaballs, only those within the group. 4. You can't turn off AA for metaballs or trees 5. Only some volume materials work with metaballs, experiment. That's about all I can think of right now.