1. Start by researching your industry online... what types of things are websites linking to? What types of press angles are being written? And how can you do similar things?
2. Keep a list of those websites from step one... so that as you do and create interesting content, you can reach out to those people for feedback and/or requests to mention (link to) your content in the future.
3. Ask yourself which websites that your prospects spend time on... and then devise a reason those websites would WANT to link to you. After that, begin pitching them. It's a sales process like any other, so it will require some testing and amending then re-testing. But if this is your business, the job of your marketing department is to figure that out.
4. Get help from consultants as needed, to save time. Not just for marketing of course- but find people that have accomplished exact or similar goals. Investing small amounts with these people can save you months or even years of learning curves :)