If you have never employed staff before, check out the gov.uk guidance.
Almost all of the questions we get asked are answered in a book published by NCVO, The Good Guide To Employment. There is a copy available to read in our resources library.
We are often asked about the differences between employing someone and contracting someone as self-employed or as a casual worker. The different roles are explained in guidance on gov.uk employment status. You can also use the Employment Status Indicator Tool.