kevlar551

what is a simple way to prevent contamination while i am growing bacteria because yeah I do not have a high tech lab being that this is an 8th grade science project.

Hello, I am working on a science fair project that involves growing bacteria in a Petri dish. I am going to build an incubator and would like to know how I should go about growing the bacteria. Should I just plop the samples in the incubator and turn it on, or is there more to it?