When you reach certain milestones on Facebook fan pages and other sites, you gain access to analytics, insights, and other metrics. Your website should also have this information. Even if you are not a numbers geek, this data is valuable to you. It shows progress and gaps in your marketing efforts.
While you shouldn't fixate on numbers, followers, retweets, and likes, you should use them as a measure of the post you're creating. Writers also need to remember the social part of social media. You need to build relationships and followers by interacting with each other. If you only use these sites to dump announcements about your reviews and sale items, you're not going to be that successful.
Facebook and Twitter offer a lot of good information. You can see things like which day you get the most traffic. Target those days for posting new material. You can also see which posts get shared or commented on the most. This can help you figure out what type of content works for you. Facebook gives you a lot of information, including the age group/ demographics of your audience. Twitter tells you your reach for the week. You can see which tweets get the most action, and how many lead to link clicks. You should use Twitter and other sites to drive traffic to your blog or website.
If you boosted a post or ran an ad campaign, you can see the results. This can help you decide which types of posts to pay for next time.
Your website should also have metrics you can use to track visitor patterns and what types of content are most popular. I use Bitly to shorten my blog URLs for posting on social media. It has an analytics page that lets me know how many people have clicked on that link and on what days. My website visits were up and down until I committed to post a weekly blog and post links to it on Google+ and Twitter. My Google+ numbers aren't as high as my Twitter ones, but they do help me with my placement in Google searches (SEO).
The charts, graphs, and information can be overwhelming. Start with one item like your reach or the key days of the week. If you need help, Facebook and Google have good help files that explain what the numbers and different charts mean.
All of this information should help you decide what's working for you. If you're scheduling tweets, and you're not getting a lot of retweets, replies, or favorites, then you probably need to look at the content, frequency, and timing of what you do. You're doing a lot of work for not much reward. Also know that if others looks at your recent tweets, they can see the action or inaction too. Mix it up and see if your numbers improve. Make sure to add a couple of relevant hashtags to get the attention of interested readers.
Also note that Facebook changes its algorithms frequently, and this affects what your friends and fans see. I wouldn't depend on it as my only marketing method. To date, I haven't paid to boost any posts, but I'm working on a marketing campaign for my first solo mystery for next spring. I'll let you know how that goes.
Finally, there are way too many social media sites to have an active presence on each. Pick what your readers like and focus your time there. Don't let it overwhelm you. Make small changes and see if your numbers improve.
Happy marketing! And let's connect so we can build our reaches and resources.