If the above is the case for your site, I would recommend that you read Have your organic search rankings dropped immediately, as you need to know sooner rather than later where your links are coming from.
There are books dedicated to this subject, but in short A good social media strategy is an excelent way to get good quality inbound links, for example: a video on youtube, some pages on facebook, tweets linked into new pages on the site. Ensuring that google +1 is properly implemented is another.
Also, it is good to try and get links from high quality sites, maybe from PR events or news articles. Take a look at what your competitors do, especially ones that are more successful than you are in the search rankings.
Before building out new content, time should be spent working out what people actually need. It’s no good building out lots of new content, only to find there’s only a handful of searches for that every month, and there’s already lots of competition.
In order to identify which content in your specialist subject area would be most useful to people, you can use the ad-words keyword tool, SEM rush or other similar tool. These tools will give you an indication of how much competition there is for each set of keywords.
Strange name, but very worthwhile policy. Many searches that arrive at your site will be for three or more keywords. These types of searches have less competition and for smaller sites it’s easier to compete. I always recommend to go for longer chains of keywords rather than single words. This is often referred to as the long tail search and leaves your site less at risk than having two or three big keyword searches.