How to do effective marketing of a software design and development company to win more clients/projects?

We are a small software design and development company with expertise in the areas on facebook apps, iphone, android apps development. Most of our clients/projects have come from sites like Elance, oDesk etc. However we want to grow from here and expand our client base. What avenues should we go for effective marketing to get leads? Google Ads? LinkedIn Ads? Cold calls? Any other ideas?

Much appreciate your suggestions.

Probably adding a blog to your website with both technical/business type articles would help. Then syndicating the blog thru the social media machine (linkedin, facebook, etc). On your blog or site you should be able to collect email addresses and send out whitepapers from time to time.

Since you are targeting people with development questions, if I were doing this my route would be to go to stackoverflow, Android stack, etc and start building up a reputation for knowing what you're talking about. Don't push your services onto people, everyone hates that, just link to your company in your profile and let people look themselves.

This route solves two problems: 1) It targets people struggling in the specific domains you want to offer your services and 2) It proves to your potential customers that you have expertise in that domain.

The problem in your field is there are literally thousands of small groups in Pakistan and India offering development services. I've tried very many and it's always the same, they claim to be experts and after 5 minutes talking to them, they clearly have no clue about the subject. The stack overflow route would go a long way to allay this very common concern for companies looking to out-source. But you will need to spend several months of producing skilled answers, not just spamming answers for reputation.