When it comes right down to it, the goal of SaaS marketing is the same as any other business marketing... leads. Your marketing team needs high-quality, sales-qualified leads to pass along to the sales team. However, as a SaaS company you do have a few unique oppotunities for marketing in addition to the standard methods.
Having relevant content on your website is a must for two reasons:
The buying process has changed dramatically in the past few years. Buyers research products and actively seek out solutions to their problems. Those who speak directly to solving those problems are the ones who get the prospects.
Search engines, such as Google, are looking for sites with robust content that matches search inquiries. Gone are the days of keyword stuffing and link building just for the sake of ranking number one for a keyword. User experience is what search engines look for.
Relevant content that you could (and should) use as part of your SaaS marketing strategy should include eBooks, webinars, blog articles, videos, white papers, case studies, etc. Chances are you have a ton of this stuff just waiting to be properly leveraged to generate new prospects for your sales team.
While the old model of VARs (Value Added Resellers) and ISVs (Independent Software Vendors) may only be appropriate for SaaS companies with the Enterprise sales model, it is still possible to leverage service providers as a means of scaling your business. SaaS companies with a more complicated software, such as Salesforce, can utilize a "certified partner" model that pays a commission based on the type of license sold as well as having a partner to successfully implement the software. These partners will actively seek out new leads to build their business, and yours, in the process.
For less complex software, developing an app for app stores such as Google, Apple, Intuit, and Android is another opportunity to explore for SaaS marketing.
Using "refer-a-friend" as a means of generating new leads can also be highly successful. DropBox is one such example; their program generates not only new leads but customers as well. Other companies using this same type of program are EventBrite, Digital Ocean and Elance. Be certain to manage these programs correctly, however, to prevent fraud and revenue cannibalization.
Tradeshows, of course, can be a method for generating leads. But many SaaS companies also create their own events such as user summits (HubSpot's Inbound Conference for instance), user group meetings that include non-users, even lunch-and-learn workshops can provide you with a fresh batch of prospects. These events can result in a rather expensive customer acquisition cost, however.
Running ads through AdWords, Facebook, or Linked In can be effective if you have a definitive plan for how to handle leads from the ads. Even then, your success in customer acquisition may vary depending upon the complexity your product. If you have a fairly simple, consumer-type product, then paid advertising may result in a relatively low customer acquisition cost.
However, if your product is more complex, you may want to direct ads to a white paper or blog article. Depending upon the length of your sales cycle, this can become fairly expensive, but can still be effective if you have a lead nurturing (aka drip campaign) plan in place before you run the ads.
The take away here is that no one method should be used for lead/prospect generation. Having a SaaS marketing strategy that encompasses both quick lead acquisition through paid advertising as well as long term content strategy will serve you well in the months and years to come.