Trip to Philippines... (Manila)

Hi All,

I'm planning my trip to Philippines for December/January because I'm very curious about this beautiful Country.
I'll land to Manila in December and I was wondering if anybody has tips/suggestions etc...

A friend of mine is diving instructor in Mindoro, I'll visit him but after that I have no specific plans. I'm reading about Philippines these days trying to plan somehow where and how to spend my 20 days....

Thanks a lot for reading and looking forward to be there!
Andrea