If you are not already doing it, you should be varying your link building to include at least a few a month from this list:
Niche Business Directories
Social Media Posts
And do not get drawn into the NOFOLLOW vs FOLLOW debate. Your link profile must be varied to avoid Google penalising your tactics. For example, do not set up 1000 links with the same anchor keyword like ‘best video production service’. That will flag your site for investigation, and this has been the case since Google introduced its algorithmn changes in 2012.
Are you checking your current links?
Perhaps you may not be aware of dead links to your site where pages have moved, or been removed.
You need to avoid 404 errors across your site so grab the free SEO Screaming Frog tool and do a scan.
And dead links are everywhere and provide an opportunity for negotiating or simply adding your link to make it live. Wikipedia offers a good source, and LRT tools explain it easily.
Check also Wikipedia’s dead links
Did you ever think about using Wikipedia’s dead links as a link building source? Google finds Wikipedia to be as very trustworthy site. You can find dead or broken links there and forward or replace them. A good, free tool for this is Wikigrabber. There you can search for keywords and get the pages that require a citation on Wikipedia or have a dead link on them.
Even if the Wikipedia links are NoFollow links, they still pass on a lot of trust. Don’t think that Google doesn’t look at NoFollow links. It does since we’ve also seen them mentioning NoFollow links in Manual Action penalty claims. Read more about NoFollow links in this research we published here.