How do you build a moulo 8 decrement counter with D types, I can build it with JK's but i cant get a grip of it with D types, do you still use the and gate?

 

To make life easier, use the not-Q outputs. That way you can just do an up counter, and the outputs will effectivel decrement.

D flip-flops latch the state of the D input when clocked. A D flip-flop will toggle with each clock when not-Q is tied to D.