Confusing 的 with 得... HELP!

Hi! 

I'm studying first year Mandarin at uni and I find I'm always confusing the grammar particle 'de' 得 with the subordinating particle 'de' 的 when I try to construct sentences.

Does anyone have any hard and fast rules I could follow to pick the right one? Or is it really a matter of remembering each situation?

谢谢你！

Murray.