WordPress lets you choose the link structure for your URL’s for posts, which is really cool and handy. Here’s a permalink structure I use on a lot of blogs:
That lets me see at-a-glance the year and month of the post, then the post id, then the post title. The URL would look something like this:
The most important part for SEO is the post title, and the rest helps male a URL that is unique without getting URLs like:
Imagine you have a post titled Tips for Gmail and you do 2 of them, and your permalinks do not insure unique URLs, then you end up with something like the 2 above.