You mean hide folders from other peoples' accounts, or hide them from people that might be on your account?
If it's the former, simply setting the correct permissions will be fine -- ask and ye shall receive instruction. If it's the latter, well, that's a bit less simple. If you rename a folder to have a period as its first letter (you can't do this in Finder for this very reason), then even you can't see it.
That would be done by opening up Finder, clicking on the "Applications" icon on the left side, then clicking "Utilities" and then "Terminal." Then type
assuming that MyFolder is in your home directory. If it's not, you're going to have to <cd> (change directory, in Unix-speak) to the appropriate location and then repeat the command.
(whew -- it's much easier to talk someone through something like this over AIM)
But yeah, OS X is extremely different from Windows... if you're only used to MS operating systems, it's going to take you a couple days at least to understand how to get things done. I was lucky because I was a Linux user before I switched, so it only took me a few hours to find the rapture of it all.