Facebook and Twitter chats are underused job hunting tools. There are lots of local groups sharing job opportunities on Facebook if you search by job type and location. Also don't forget Twitter chats. These are regular, often weekly online conversations built around a theme, a set of questions and field of work.
Stick to creating profiles on popular social networks: for the moment you're better spending your time on the established networks for networking and recruitment purposes. The bulk of potential contacts will be there and are comfortable using it. Meanwhile, I'd recommend keeping an eye on new sites, but don't spend a massive amount of time there searching for a job until they're more established.
Clean up your online profile: first, if you are planning to use your current personal social media account for the purposes of your job search, I'd advise clearing up any digital dirt. Any photos you'd rather not be judged on, any comments or interactions that could potentially reflect badly on you etc. If you are using a separate social media profile for this purpose, then make sure your privacy settings on your personal accounts are set accordingly. Also complete your social media bios so that they give any visiting recruiter a clear idea of your skills, experience and ambitions.
Should two types of jobs go on one online profile? It largely depends on whether your freelancing is closely related to your job in terms of skills and experiences, if so, I would definitely keep them all in one profile. And even if not related, then I would suggest having both in one profile as having different interests will make you come across as an interesting and rounded person.
Use LinkedIn to highlight achievements outside the workplace: such as awards, voluntary activity and personal activity that might be relevant such as captaining sports teams. You can re-order sections so that this goes near the top. In particular, the personal description should be carefully thought through - this is your window to show people how you think about yourself.
Keep an eye on relevant jobs through targeted Twitter feeds: jobs sites and some corporate companies have career Twitter pages. You can raise your profile by following (and messaging) relevant hiring individuals as well as ensuring your LinkedIn profile is up to date and filled with great info so that you are at maximum visibility.
Remember employers will look at your social sites: it is very possible that they will look at Twitter and Facebook to see what you post and learn more about you. You don't need to get rid of your photos. You need to make sure, however, that your photos are not inflammatory in any way. Your photos should not be embarrassing or compromising. We all have a personal life; this is a window into who we are. You just need to be cautious about what you post and make sure it is clean.
Be polite when approaching recruiters online: as well as being pro-active there is protocol and social niceties to observe. I have seen people on Twitter rather aggressively approach recruiters and when you see their timeline it's like a constant barrage of the same question sent to multiple people. The interview and potential recruitment starts the moment you follow a recruiter on Twitter, so make sure your profile, timeline and any subsequent tweet to them is professional, courteous and plain nice. Say thanks afterwards as well.