Did you really mean this?
I'm sharing internet connection with others by using the same router. I happen to be connecting wirelessly, but I think my issues would exist even if I were wired.
Issues are: (1) I don't want them getting into my files; (2) I don't want them seeing where I'm going on the internet; and (3) I don't want them to see what I am entering when I go somewhere on the internet (i.e. user names and passwords).
Looking at Coryphaeus's reply (two above yours) I'm confused about how sharing controls work. Seems to me they overlap. For instance: if I have 128-bit encryption and password protected sharing turned on, then no one who does not have a User Account and Password on my PC can get into the files on my PC -- correct? So in that case my files (at least) would be protected even if Network Discovery, File and Printer sharing, Public folder sharing, and Media Streaming are all turned on -- correct? Of course I would still be concerned about whether they could follow me on the internet.