Many companies will use Facebook to generate some interest, but it might not always be the most effective medium. Yes, it is good for sharing general content and for creating a 'buzz' but there are some limitations. For instance, a company's audience might not be on Facebook for one reason or another. That said, it is still worthwhile at least considering having a Facebook page as you can easily post images, videos and web links.
Using hashtags on Twitter can also create interest around a topic. TV programmes and sporting events use them to create a community and businesses can do the same with new products and services.
LinkedIn can be tricky. Many companies are unsure of how to use it and how it can benefit them. LinkedIn's blogging platform, Pulse, is a key feature of the platform. It can demonstrate thought-leadership as well as educating prospects as to why they might need the company's services.
There are other platforms to use, such as Pinterest and Instagram. I would suggest looking at where your customers are and see which platforms would generate the most interest.
Piggy-backing on current events might get some attention, however it can be risky. There are many instances where individuals and businesses have been criticised for using a topical event for promotion. I would advise looking at the seasons and calendar events rather than topical ones to avoid this sort of situation. I would also advise steering clear of political posts for the same reason.
Humour can be great for showing your company's style, but be wary of how your posts could be portrayed. It is advisable to stick with light yet formal content if you are unsure.
It also goes without saying that posting content about what you had for lunch or your cat's latest antics, while humorous, are not appropriate for a company's social media.
Getting the balance right will differ for various businesses, but one in the morning and one in the afternoon is a good foundation. Again, look at where your prospects and customers are and when they are most active.
Figuring out when to post is a case of trial and error. Fortunately, there are plenty of analytical tools to help with this.