Hmm, let me see.
I use Twitter a lot, (as you may guess from my followers which I am proud to say I painstakingly acquired through hard work). I use it to interact with people, as well as drop snippets of info about my book. I tweet a lot about other people's work, and they generally return in kind, meaning if you use your 140 characters wisely, you can reach a far larger audience than just your followers.
Sales wise, I really can't comment yet, but I can say that the last 15 or so books (with the exception of
@Karen Gray and
@Island Writer) have all been because I saw a post on twitter from someone, and it caught my attention. I have also been invited to write in a charity anthology next year, again thanks to Twitter.
Outside of the internet, I can count my friends on one hand. I used to have so many 'real life' friends, but you tend to find when someone gets ill, they tend to fade into the background, especially since you suddenly find yourself with little to talk about and not able to 'meet up' as often, if at all. (A few years back now my hubby was really ill and given weeks to live. He is still with us now, but still requires a lot of care and support) My point though, I do have one, is that I already have a number of pre-orders for both of my books. Nothing massive, but I can guarantee if I wasn't using social media I wouldn't have had them. It has given me a chance to connect with readers.
Time wise I probably commit an hour or less a day to Twitter, I use this to follow back, re-tweet and engage with people, but I don't do it all at once, I have a cup of tea, my phone comes out for five minutes. the exception being Wednesdays and Fridays when I do shout outs to followers.
Facebook on the other hand, I tend to just pop on there every now and again to catch up with people who I knew that have moved to other countries. Also I find that with Facebook, they limit the people who see your posts, so even if I do post something, there is little chance people will see it.
LinkedIn I don't tend to use, I have an account, add people back, and have my blog auto post to it. When I get chance I endorse people, but that is about it.
All in all, I think, for me, Twitter has been a worthwhile venture and I have connected with numerous authors and found lots of new books that I otherwise wouldn't have come across, since I have found people, I can only assume people will too find me