Generally speaking, if you’re submitting articles for your website, or your clients’ websites and you’re including links to those websites there, then that’s probably something I’d nofollow because those aren’t essentially natural links from that website.

If you are journalist, you might be writing about a web site in a natural way… that is of course, okay.

Think about whether or not this is a link that would be on that site if it weren’t for your actions there. Especially when it comes to guest blogging, that’s something where you are essentially placing links on other people’s sites together with this content, so that’s something I kind of shy away from purely from a linkbuilding point of view. I think sometimes it can make sense to guest blog on other peoples’ sites and drive some traffic to your site because people really liked what you are writing and they are interested in the topic and they click through that link to come to your website but those are probably the cases where you’d want to use something like a rel=nofollow on those links.