If it were me I'd probably start by thinking about a location. Where is the movie going to take place - in a boatyard, a bus station, a taxi rank, timber yard, shop, etc.? Then, having decided on the environment I'd start thinking about who would be there, what are their roles, why are they there, and how might they interact with one another. Then the ideas should start to flow.
Hope this helps.
yep i think "iceaxe" has hit the nail on the head. Atlot of silent comedy is slapstick which by it's nature is a visual enviroment based comedy....think Buster keaton, harold lloyd.....and bringingup to date "Mr Bean".
Take 1 imcompetant well meaning fool palce in cakeshop,building site etc etc ...let the fun begin cakes in faces , feet in buckets and people turning round with props smacking people repeatedly in head!
hope this is of some use goodluck