Something about GPA and ECs, plz help me.

<p>Hi, I am a student who just immigrate from Hong Kong and I am a junoir in a High School. I am taking 4 AP class, AP statistic, AP Chemistry, AP Physics and AP English.
Actually, i have two question to ask.
First, as i am a student who just came from Hong Kong, i am not sure about how to calculate my GPA. I get all As in the current grade of subject besides AP English(the teacher is really strict, there is a semister that no one got A in his class.) However, the scale of grading is different in HK, it is rarely to have an A. Almost all of my classes in HK are Bs or Cs. Will it affects my GPA to a large extent?
Also, I also find it difficult to join any outside activities here, can you guys suggest how can I join those clubs or activities, what are the activities that colleges are looking for? I am a soccer team player as well as a orchestra player in my previous school, i speak fluent Cantonese and Mandarian.
By the way, I love Stanford, it is my dream college. She is the reason for me to scrafice the chance to enter University of Hong Kong and immigrant here. I might also apply for UCLA and Berkeley.</p>