For the time being, StumbleUpon is still doing quite well at driving traffic to sites. We can attest to that first-hand. Here are a few tips that may help your content do better:
1. Create content that people are likely to find entertaining, interesting, important, or just plain cool.
2. Build a network of StumbleUpon friends.
3. Don’t just stumble your own stuff (though I personally don’t think it hurts to do it sometimes). I wouldn’t do everything you create though.
4. Find things that haven’t been submitted to StumbleUpon yet, but you think others will find interesting, entertaining, important or cool, and submit them.
5. “Like” things that have already been submitted that you find interesting, entertaining, important or cool.
6. Use as many relevant topic categories as makes sense when submitting something. This should help target it to the right crowds.
7. Reviews are optional, but it can’t hurt to write them.
8. Making content visually appealing with use of pictures or videos can lead to more stumbles.
9 . Use the Stumble button on your content
10. Promote your own StumbleUpon presence.
11. Use StumbleUpon’s paid options.