Eric,
Typically most schools are looking for someone who has a degree and a TEFL/TESOL Certificate or an equivilant certificate. But, I have heard of schools who hire teachers without certification but with teaching experience, how many years varies from school to school. Then there are the schools who will hire any native speaker who walks through the door!
Here's the address of an online group of English teachers in Poland, they often have job listings and other useful information like Visa requirements and stuff:
polang-jobs@yahoogroups.com
Good Luck, Emily
PS There's a bit of snobbery here about British English vs American English so if you're British you're in luck!