Create a Account over FB & Page with your profile pic and professional details .
Join various groups In your niche having atleast 5k member list and those groups are active .
Like pages .
Not only your service gig link post some informative content also and your thoughts .
Engage yourself in Discussion on top pages , group and after some replies you can leave your service link .
Try to shorten your service link with goo.gl so that you track the traffic from where you are getting traffic on your link .
For Twitter as you know you can post only 140 words so you have to be more specific in your Tweets ,
Retweets others big profile tweets .
Do follow-unfollow method for getting good number of followers on your profile.
Try to post Info-graphics explaining your services cause Images catches clients more easily then a long descriptive sales thread.
Leave some space in your Tweet so that others can also RT your tweet .