awesome question! I was always a little offended when people grabbed a big nug and just crushed it into the bowl...

personal method, actually I like that term "size of pencil erasers", one nug around that small in the bottom of the bowl to hold everything, then a little bit finer grind on everything on top. Gets going nicely, and the nug in the bottom burns a bit slower for a longer smoke. Though, I only smoke by myself when I've got the mary, and friends tend to hit "genie" as hard as they can ;-).