How to raise my gpa and how to get into grad school?

Hey guys,

I am a Math major, BS and my gpa is like 3.1. But I plan to go to a really good grad school such as abroad (like in Europe). What are some ways I can raise my gpa? and get into a good grad school? I want my gpa to be a 3.9 and am planning to work on my second degree? but eventually I want to go to harvard one day. so what are your suggestions? Thanks!