When you've decided on a course of action for your blog, you'll need to name your blog. This can be fun or laborious, depending on your love for puns and creating headlines.
You'll want to choose a name before registering your blog. In fact, you'll want to choose your name sometime after you commit to the idea of blogging and have chosen your blog's focus.
You want a name that relates to the theme/focus of your blog, isn't too hard to remember or spell, and isn't too long. (Check the resources for more tips, opinions, and bad examples.)
Before you register, you should make sure your clever title isn't already in use. Many blogs are protected by copyright, and many bloggers will sue over use of their blog title. (And in some cases, rightly so. You'll usually be politely notified as to the infringement first, in which case you should just apologize and find a new name.)
So before registering your blog, Google the name of your new blog. Try other variations as well. For example, in addition to Lessons for Old People I might try Teaching Old People About Stuff and Technology for Old People. I also input my search as "Lessons for Old People" (so Google would search for the full title) among other variations. When I was absolutely sure that no one else had been struck with brilliance and named his or her blog Lessons for Old People I was ready to move forward.
It won't be too long before you're ready to move forward, too!
10 Quick Tips for Naming Your Blog Blogging Startup (Note: I disagree with number 10. This can still conflict with a copyright issue. For example, you could never name your blog Purple Dooce and get away with it.)
How to pick the perfect name for your blog or startup, CNN
What Not to Name Your Blog., Slate