multiple condition queries

morning all

hopefully someone out there can offer some assistance

i am building an access application in which i wish to be able to intially
look at all the data in a form view (sorted that bit out), and then be able
to use a variety of drop downs to "filter" the data based on if anythng is or
isnt selected in the drop downs

ive got all the drop downs sorted out the problem comes in the query.......
I want to be able to use 1 query and in that where i have a field i can
either filter on it or not

at the moment i have like "*" & [filter value] &"*". however this does not
bring back all the results. How can i have it that this is bring back
everythign or filter as required

thanks

stuart