Latest Update: Linked to Gina's excellent answer to ProBlogger's One Question Interview.

If you've got a blog, you probably want more readers, no matter why you're blogging. If you want to make money, more readers means more income. If you want to 'sell' yourself or your services, more readers means more 'sales'. If you just want to communicate with people, more readers means more communicating.

Tips

• It takes time - you can't start a blog and get hundreds or thousands of visitors straight away. Some people can, but usually only if they have something to leverage to get there - maybe they're well known in their field, of they run other related blogs they can bring readers along from. If you don't have any jump start, though, it takes time. Google won't send searchers to a new blog until it's been going quite a while, because there's too many spam blogs out there. It could take a year or two (or more) to build up a significant number of readers.
• Choose your subject wisely - if there's plenty of other people already covering it, you'll have a hard time breaking in. If there's not enough people interested in it, you'll never pick up a lot of readers. And whatever you choose, you're going to have to spend a lot of time on it for quite a long time to come before you start to gain much back. A smaller niche is often better than a bigger one - it's easier to get 'fans' in a small niche, then build out from there.
• Start with the right platform - if you're going to try to make a go of it, don't start with a free Blogger account. Get yourself hosted properly, and use something like WordPress or Drupal.
• Talk to people - if people take the time to post comments, take the time to respond. Make them feel loved.

Tips Elsewhere

• Gina Trapani: What would I do different if I had to start my blog over? - from ProBlogger's One Question Interview, Gina gives a list of answers, including some good tips, mainly about thinking more about the future when you post - it's easy to forget that what you post today will be around for the rest of your life. I'd add trying not to let that make you too nervous to post anything.
• Ten Tips for Writing a Blog Post from ProBlogger.
• 10 Journalism Tips for Bloggers, Podcasters and Other E-Writers from Spencer Critchley at O'Reilly. Useful tips if you're approaching blogging from a journalism point of view.
• 19 Lessons I've Learnt about Blogging from Darren at ProBlogger - lots of things he's picked up, and Darren should know - he makes a decent living from blogging, and part of that is through helping other people to make money from blogging. (It was this article that inspired this page.)