As NotAllThere said no flash photography during Morgenstraich

Add to that:
Get your blaggede (sp?) and wear it prominently
Don't throw confetti at the cliques as they parade
Don't get in the way of the bands as they march

otherwise can't think of any others...

Re: Downerbuzz's post: there are two groups of folks in Basel - those that love and those that hate Fasnacht, with little in between. That includes folks from Basel as well...