There are many ways to do this and there wouldn't really be any point in showing you one way or another because in the end individual examples don't teach the ideas behind techniques. The basic idea is to be able to take some data input into the system (by a form, etc.) and through some method screen, filter, examine it to verify that it is something you are willing to allow into the application. There is no "best way".

With regards to host settings getting in the way of scripts, did your tutorials give any examples of individual settings which might be a problem?