If you're going to have to roll up your sleeves and get links in-house, you need to ensure that the links you're targeting are worthwhile.
As I mention frequently, external links to your website are one of the two magic ingredients which get you high up in the Google results (the other being the presentation if your pages). This is really frustrating to most busy marketing managers, because it's not something which can be easily outsourced. Why not? Because the very best links come from spotting the opportunities and then reeling them in through good old-fashioned personal contacts. If, for example, you realise that a terrific website from which to get a good link is that of a specific trade association, then it's almost certain that the only way you're going to make that happen is by direct contact from within the company. Some third-party agency or consultancy is hardly likely to be able to persuade the trade association's website manager on your behalf.
Similarly, good opportunities for links might be from your own suppliers. Again, "SEO consultants" aren't going to be the people who can get these set up: you are.
So if you're going to have to roll up your sleeves and implement this programme in-house, you need to ensure that the links you're targeting are worthwhile. If you've spotted a website which you think might link to you (given the right incentive), you need to consider if it's worth the effort. A link from a single website which is highly-rated by Google can be more valuable on its own than links from hundreds of sites which aren't.
Many specialists use a free "SEO toolbar" created by the SEOmoz website called MozBar to assess sites and individual pages. Once installed, the toolbar shows you a rating for "domain authority" and "page authority"; here it is on our own website:
The MozBar also shows site and page data alongside Google searches, so you can start to query Google for relevant search terms and see the best sites out there. Some may well be opportunities you hadn't considered.
Once you've targeted a site which seems to be influential and with which you think you might be able to get a dialogue going, it's time to consider why the site might want to link to you. Nobody's going to make an update to their website unless it's for their own benefit. You'll need to have something worth linking to.