Which white-hat link-building methods are most effective? And please share some good services that offer this. 

Of course guest posting and press releases. The latter is something I can personally recommend as I had a great experience with it. Though you should know good places to get those, as quality of the donors has major affect on your ranking. And I will recommend a good place to get quality press releases. Here's the link www.brandpush.co . Click it and you will find all the information you need.