Along with these technologies have come ways of engaging with customers and that's where social media has come in. There's a very good reason for the bookmakers using social media to engage their audience, the majority of facebook and twitter users are the younger generation, that means new customers.
What that means is that there are more offers available online and in social media than you'll be able to find yourself by just visiting the website of the bookmaker. There are sites where people share information, The Gambling Times, RPoints, MSE, Punters Lounge etc. but if you want to get something that's time sensitive then you need to be following bookmakers on twitter and facebook.
The best way of doing this is to set up an entirely new account for it, else you'll have your regular feeds filled with gambling posts and that might not be the best thing for you to share with your friends and family (there's nothing wrong with matched betting, but it still has a stigma attached to it as people don't understand it).
Set up a new account and follow everyone, and while you're at it follow https://twitter.com/TGT_Official as they do a lot of the filtering for you, and whilst full membership will cost you, following them on twitter will not and it'll give you a good idea of some of the offers that are out there.