Most of my traffic comes from Google, but then I run a recruitment website. We don’t get more than a couple of hundred uniques a day right now, but aim to increase that with the launch of a new site (current one is crap!)
Getting backlinks to various other sites is obviously a great way to get traffic.
I have a link in every clients footer (that allows me to, of course) with “design by: ectect” and that brings in a lot of traffic, since one of my clients is monopolizing the first 10 pages of google with most of his keywords his traffic is crazy.
Read up on some SEO, once your site is optimized and you start gaining a little traffic your results will keep getting better.
If it’s your portfolio that you’re talking about, make sure you leave the link in every comment you post on all the various design blog articles (not inside the comment, in the optional website field), nobody likes a link spammer.
Quality traffic, for something like a blog unfortunately has to come from quality content the better your articles, ideas, or content is the better your traffic will get.
You may be lucky enough to write a hit article that becomes insanely popular overnight, though for the most part it will take time to grow.