I have had a stumbleupon account for awhile now, I've posted up a number of sites / pages but have never had any luck generating traffic from it. Personally I find the best use of SU is to find great content that I can promote and use to attract people to follow me on twitter etc thus growing those accounts which I can in turn use to promote some of my own content.
It depends 100% on your content. People on Stumbleupon are bored. Its Facebook type users, looking to kill time. So you have to provide content these types of people will enjoy.
Also, you can't just Stumble your own content and expect to get anywhere. If you make something and you think it will be particularly viral, spend a couple bucks and use their Paid Discovery service. You can get a lot of stumbles for cheap, and if the content is good, it will take off on it's own.
You have to create a large number of followers on the stumble upon.People always find unique and quality content,so you can increase the number of followers by adding the new and different content .More followers will give you more traffic.
Actually, whatever may be the mode or source you are trying to get visitors from, just dont forget that people visit your website only if they need to or only if you can get their interest. So, whatever you do on any social networking websites, just make sure you post a great content and something that can grab readers interest. Moreover, visitors who dont convert are literally waste, isn't it?
So, try giving content about your product or service that can grab readers interest and do not divert their interest by providing interesting content that has nothing to do with your website or product. Try adding businesses that may need your services and bookmark pages that you believe are your best.
Content matters at the end of the day, no matter which social media site it is. In order to grab the attention of users on social media site, your content has to be really attention grabbing and intriguing. Even if its not, you've gotta make it look like one, and that is what marketing all about! Use multiple sites for SMO, do not just wind up with Stumbleupon.
I agree with what everyone is saying. It all boils down to content.
Catch your reader's interest from the first lines of the article you are sharing and try to keep it that way until the end. People on stumbleupon are mostly bored people online trying to look for interesting things. These are usually the people with short attention span.