Due to a spammer attack, I had to turn on comment moderation for posts over 14 days old. If this turns out to be inadequate, I will turn on moderation for all comments.
As for what I consider spamming, it mostly falls into one category: comments aiming solely to promote a commercial web site. It doesn't matter where the link is, in the comment or in the user name of the commenter, I consider these spam and will delete the comment. If you wish to advertise in my blog, you can do what proper advertisers do and pay for it.
However, links to commercial sites in relevant context are OK. With this, I mean comments actually related to the issue of the blog post, where the link is a relevant part of a comment (for example, a link to a doll page on a web store).
Links to private blogs and other non-commercial sites are fine as long as the site is suitable for children.