Hi Nottyqueen,
I wouldn't go so far as to call successful FB and Twitter marketing a secret... You just need to have your wits about you and a keen eye ;-)
As a user on these platforms you can see for yourself which ones are getting attraction i.e. No. of followers, retweets, shares and likes etc... Look at the content that these users put out, the type of ads which may appear on your wall or which are paid "sticky" tweets, no. of retweets and the hashtags used and checking the numbers of views for them... With that you'll see some interesting findings and perhaps some great ideas for you to adopt... You'll probably see like I have that direct sales does not work and that interesting, engaging, fun content works... In otherwords an indirect approach - which I'll come to later....
Now before engaging on these platforms I also think its worth mentioning that it is useless to attempt to game these platforms with fake purchases for followers, likes etc.... Other than than the obvious violation of terms these fakes do nothing with reaching out to real people and further such as on FB dilutes your organic reach given that FB only allows an approx 10% organic reach to your followers.... If the bulk of that reach-out is fake then you can see its going to hurt you long term...
With that out of the way... I would recommend that all roads lead to your own website... As you own the content.... but at the same time set-up enough reasonable content on those social media platforms with further reading/details when necessary to your website... So for me the main focus is my own website with leveraging these platforms.. Plus you have much more flexibility such as the ability to get people to signup to your list, buy now, secure downloading items etc...
The fact is its an extremely crowded place! Getting heard on these platforms is difficult... even if you have super amazing content on these platforms, chances are its not going to be seen with it taking a very long time to build these social media resources to that of a perceived authority.... and for the word to get out.... I personally want to take the short cut... and therefore use Ads!
With these ads I dont bother with direct selling - but my efforts relates to capturing leads through offering a free bonus in return... Something which offers values and eases the pain points of your target audience.... Once on your list that's when the relationship building starts!
So to an extent I disagree with some of the above comments with focusing on relationship building first... For me its after they have signed up to your list... Its too difficult to do that before they sign-up when you consider most people when they visit they leave and never come back ... lol... How many times have you book marked a super amazing website and never came back to it???
So for me its enough to have some good reasonable content - enough to make you look credible, but that's it... and that can be done with little effort... The emphasis is to get the lead onto your list... and thereafter my preference is to use my own website and not social media platforms for the long haul with building a relationship, providing value and above else where my offers are located....
Hope that helps! and good luck with your online endeavours!
Cheers, Sid