I just used the media tool method (http://www.microsoft.com/en-us/software-download/windows10) and selected the upgrade option and just followed the steps, it took a while to complete but went flawlessly. I guess the only thing one needs to worry about is whether to select 32 or 64 bit. My windows 7 was 64 so I just selected the same.
Which language, I chose English. Wonder if I should've picked English - International