Similarweb.com is another useful tool to see what competitors are doing.

I was helping a guy in the used cellphone resale niche for a day, and he was initially convinced a social media campaign was the next marketing step.

A check of the top three competitors on similarweb showed they are getting less then 1/2 of 1% of their referrals from social media. So this evidence quickly changed his thinking about what would be effective in a marketing plan.