Nodus is one of the best Minecraft hack clients.
WINDOWS you just simply download the minecraft.jar then press the windows key and type:
%appdata%(If you are on xp type %appdata% in run) press enter and the first thing you should see is a .minecraft folder go into that folder then go into the bin folder there should be a minecraft.jar delete that one and put the one you just downloaded in.
MAC download the minecraft.jar once downloaded open up finder at the top of your screen and press file then press (go to folder) finder should have a bar at the top of it press enter and scroll down until you find the “minecraft” folder go in that folder then go in the bin folder delete your minecraft.jar and put this one in.
BETTER MAC INSTRUCTIONS COMING SOON.