It's actually a very simple two-step process.
Step 1: Create excellent content and/or provide other resources that are interesting, entertaining and/or valuable to others. Make your website attractive and easy to use.
Step 2: Use good old-fashioned real marketing to let other webmasters know about what you have to offer.
Follow these two steps honestly and well, and traffic and links will follow.
Don't know what I mean by "real marketing"? Operating under the misapprehension that marketing only happens online, or that things like dropping links in blog comments is marketing? Have no idea how to let other webmasters know about what your site offers? Then you might need to add a Step 1.5 in between the first and second steps: Take the time to study from true marketing professionals to learn what real marketing is all about. Although some of it may take place online, it isn't exclusively online (even if you're promoting an online resource). It doesn't involve spamming or link drops. It isn't even necessarily about paid advertising, although that can be a component of it.
Is this a lot more work than collecting a lot of low quality links from directory submissions, blog comment spam, forum signatures or posting link drops, social bookmarking, blanketing the web with crappy "guest posts" on blogs nobody ever reads, and the like? You betcha. That's the point. You asked about the best
way to get links, not the easiest