I wouldn't say twitter is even related to SEO other then for building some hits. Quit spamming twitter and like homeboy above said, go the white hat route.
We must look to the Web (Twitter) for new ways of finding customers and communicating with them, rather than at them. We shouldn't try and market something with every Tweet! I suggest a 20:1 ratio. Give information away for 20 tweets then post 1 marketing tweet. Get followers to see you as someone who provides them with good information and someone they can trust and they will eventually become your customer.
i use twitter to get quick traffic!, my niche is web tool and sometime i get best click, always i use CPA offer, but now i stared to sell using Clickbanck product, and it work very well look at my review page http://url-ok.com/ec64bd
I am using twitter for some time. I think it is a good tool to talk about some topics. For marketing, many people are unwilling to buy anything from strangers on line. So in my opinion, first of all, you should own some sincere friends, and gain trust on you. Then you can build link of marketing.