TPA3100D2: related document for choosing the amp with related speaker

Hi,

i am using TPA3009D2 for my design.

1. i wanna know if there are documents discussing about how to choose proper amp? (mine is 5W at 4 ohm) , i want to know what is proper output limit to keep speaker from burned out. is there a equation or experiment suggestion?

2. is there a design guideline for the amp power and input signal level? I want to know how to keep output of speaker not to beak.

Please let me know if there are app note for these question.

Thanks for your help.