Step 1. Go to the Layout tab from the Blogger dashboard. Then click Edit HTML and make sure you check the 'Expand Widgets Template' option.
Step 2. Search for this piece of code,
Step 3. Insert this code directly below it.
<div style='float:right; margin-left:10px;'>
<script type='text/javascript'>
digg_url="<data:post.url/>";
digg_skin="compact";
</script>
<script src='http://digg.com/tools/diggthis.js' type='text/javascript'/>
</div>
Step 4. Preview and Save.
I try to submit every post to digg. If others find it useful or interesting, they will digg it as well. I have gotten a little bit of traffic using this method, and some of it repeat visitors.