Predator keyboard has 3 (or 4 or even 5) symbols on certain keys. How do I use them?

I find Acer's keyboard design to be utterly incomprehensible and can find no answer to this simple question: how do I use the additional symbols on the keys beyond the second? I get that shift gives me the second symbol, but how on earth do I use the third and fourth? None of Alt, Alt Gr, either shift key, or Fn do anything and neither do various combinations thereof. I am pretty close to just buying a better designed keyboard but would like a solution. I really need access to certain often used symbols such as greater than, less than, and approximately which are widely used and really shouldn't be inexplicably hidden within the infrastructure of the keyboard.