How can i set up a remote desktop connection so i can remotely access my PC E.G. at School or Work?

Try creating your own thread instead of hijacking someone else's.

That depends on what operating system is installed on your host PC:

If it's Windows I recommend using either the default RDP Protocol or TeamViewer.
If it's a Mac, there's a nice utility called Apple Remote Desktop, though it's not included in the OS.
FreeNX also works great on Linux.

Don't forget classic VNC. UltraVNC allows connection through any Java enabled Browser.

Hamachi, OpenVPN, ssh redirects to a VPS, configure your internet gateway to redirect 3389 ....?

ARD usually likes having ports open in your router, where as TeamViewer uses some sort of VNC over VPN that is portless (i.e. no portforwarding required!). It works on OSX, Windows NT and Linux, not to mention there being clients for Android and iOS. If you want something simple, I highly recommend TeamViewer. If you fancy portforwarding and you use Windows, I recommend you use Terminal Services (RDP). If it's a Mac OS X or Linux host, VNC works nicely (requires portforwarding). By the way, you do realise that Mac OS X has a built in VNC server, Pwned? Though I will agree, Apple Remote Desktop is excellent but geared more towards the enterprise section rather than the typical home user. I think that W8BF is wanting a simple service.

Both RDP and Apple Remote Desktop require opened ports, but not if you're using Hamachi (or any other VPN).
VNC is a little bit outdated (it's streaming a set of compressed JPG images after all), I've seen much better enthusiast projects, which were doing better than it.
TeamViewer is good, because it uses P2P, so no port forwarding, also compresses the video I/O very well.

And no, I didn't know that OS X has VNC by default.

Take a look in System Preferences > Sharing. It should be labeled as "Screen Sharing"

Yes You need to make sure remote desktop is enabled on both PC's, depending on the operating system vista and 7 you can right click computer-->Properties-->remote settings, from there you allow remote connections less secure. That needs to be on both machines to allow the traffic to RDP. You should static assign an IP on the computers, so the IP doesn't change when other devices connect to the network. IF you have a wireless router you will need to forward a port to the IP assigned to the PC connecting to.
Google how to setup and configure RDP. Or as someone else said you can use team viewer, however team viewer is a desktop sharing program, and times out on you if you use it to much.

No, just the host PC you want to access needs Terminal Services enabled.

I tried all kind of different ways in the past time but I have to admit that now I find TeamViewer to be the easiest solution especially for my mother who knows nothing and is just waiting for my help and it works through your network without having to tweak it.

Here's a second for UltraVNC if you don't just use RDP. Even RDP has an ActiveX web client somewhere. I think it at least shipped with Server 2003.