- Keys: authenticity, transparency, humility, respect
- Medium: c-c-c culture character characteristics, proclivities, demographics
short. real-time. contextual. customer support. news breaks on twitter. Corporate and personal are both received well, but pick one. If you're not on top of your stuff, your message will probably be lost. twitter moves quickly, and waits for noone.
longer, but still <100 words. Photos a plus. If your tweets are high quality enough, cross-share them. It's a personal network though, so be personal. Don't be business. Specifically, trumpeting brand messages and slogans does not seem to do well here. Again, it's a personal network, so personal interaction is key. B2B is not easy here, due to the personal nature of the network.
long-form writing is possible (and you'll find others quickly if you do). It's good for meta-discussion. Photos/videos/thought-leading(saying the right thing to the right people at the right place at the right time in the right way) with high quality links to outside articles marked up with Authorship/hCard always a plus. G+ loves high-res photos with relevant text. Communities are absolutely gold if you want to work on the meta-discussions around branding, marketing, coding, web design, web development, whatever. It really doesn't matter. Someone, somewhere has a community around the topic you want to work with. Unlike Facebook, penetration is not an issue here (Facebook filters messages (unless you pay) while Google has attempted to build a serendipity engine). Also, be aware that anything you put into G+ with links and photos and discussion will boost that link's rank. Google has been about as clear as you can be about what G+ does for sites.
The internet tells me this is the one for B2B, but I have zero experience with it and thus cannot speak to its advantages. But — It's the business professional's network for a reason. Businesses are here.
I don't know about Bing and others, but Google has, for the past ~2 years, been moving towards punishing all of the old SEO tools (see all the articles that come out every time Google pushes a new search engine ranking algorithm. The algorithms are named, and every time SEO people scream bloody murder. It's great). All the keyword spamming and loading, all the link-building, etc. They want real text written by real humans, attributed to the real author (Google Authorship+hCard data). Use all of the new html5 micro-formats, all the little things like hCard data, along with excruciatingly good, well structured, semantic html5. Even if some of the old tools work still, the general trend is that Google wishes they didn't and is working to make that a reality. Best not to waste money being on the trailing edge.
Don't cross-share between networks if you're saying things targeted to that specific network/demographic, and also not if for example your twitter is business and your Facebook is personal. Those shouldn't be automatically cross-shared between. Manually, perhaps.
If you share gorgeous hi-res photos of work, any of them will do, but mostly the sites other than twitter. (twitter likes links. photos are fine, but (a majority) use it on a mobile phone.)
If you're going to work ~8 hour days, an hour of that should be industry(social+networking) stuff. Keeping up with news, making commentary, pointing out issues with new stuff, etc. Be original, give your opinion, etc. You want to be a part of the meta-discussion. It'll help you stay informed about new stuff, and you'll pick some leads up in the process (especially if what you're saying is spot-on). (being spot-on is often called being a "thought leader" in a marketing context. The right thing at the right time.) When you die on the internet, you die for real. Friends/acquaintances made on the internet are no different. Make them, keep them. This also means that if you fuck up, you fix it. Keys at the top should guide your interactions.
what kind of prose will you use? what tenses to refer? what will the voice be like? company needs a "voice". clear separation is the most important thing. Business * page should be only things you want to reflect on your company. If you and your brand are synonymous, then you're synonymous – see previous sentence.
When at a certain scale (large enough where social media is monetarily worth it to support during business hours) perhaps set business pages up to be run by someone whose job it is to do that. This way it's not a personal thing, they're representing the brand. This can only happen after the questions earlier regarding the company's voice, etc, are answered and documented.
you like branding: so show-and-tell examples of really good branding. Not a bad idea for a blog, either (weekly? so you can dip your toes and gain an audience without a massive amount of time spent on that single outlet). G+ would like it, too. This is not "hey look at pretty pictures" – it needs to be more substantive. If you want to go for it, do something longform such as critiquing fully the designs, laying out where you think their influences came from (think art history), things like that.
random: average WordPress post is 280 words, top 200 best twitter presences respond to users in ~14 minutes, on average.