Information on basement dig

first time digging a basement gotta do it some time. I have friends that are experienced and going to help out, I didn't plan on it but bid it and got it. Have questions about digging the footings and finding grade 9' walls, 6" floor. How deep does the footings need to be and how wide? It's a 41x46 any info will be appreciated they don't have any plans on grade or any surveyors going to be me and the concrete guy laying it out.

Information on basement dig