Your absolutely best and most effective marketing strategy is to create such a satisfying experience that your clients are happy to repeat and refer their friends -- then you build on this process by encouraging it and systematizing your approaches to building out the repeat and referral interest.
Social media can be especially effective in building your reputation BUT you need to be on the ball, because negative publicity can spread like wildfire and you won't have much time, if any, to recover if you screw up.
You can learn more in my Construction Marketing Ideas book. (Yes, a bit of unabashed self-promotion here, but you can read the reviews yourself and if you wish, write your own. The book is as inexpensive as $20.00 in online format.)