Start with www.tumblr.com.
This is what the screen looked like in mid-June. It may have changed since then. (It may change again!) CLICK SIGN UP.
Fill in the blanks. Provide your e-mail address, password, and desired blog URL. The URL you want may already be taken, so this may take awhile. Note that you can change your URL later. (Blogger lets you do this too!)
...This is all you need to do to sign up for an account. (I know, it hardly warrants a post, but that's how I roll.)
After Tumblr warmly welcomes you in to its community, you'll be asked to do a lot of stuff right away. (A lot of stuff I could have turned in to individual posts.) While you do that, Tumblr will send you this e-mail:
While you get set up, we wanted to let you know about a quick way to post to your blog from right here:
Just send an email with text, photos, quotes, or MP3s, to [redacted] and it will appear. You can even send photos or texts to this address from your phone. Try it out, and make sure you add it to your address book!
For more info: http://www.tumblr.com/docs/
For more ways to post: http://www.tumblr.com/goodies
Now let's fill in the blanks on your new account!
This is what you see after Tumblr says howdy. That's your dashboard beneath the bubble. You can click the X in the corner of the bubble if you're not ready to write your first post.
This is what's next. You can easily customize your blog right here, right now. Fill in the title for your blog and upload a photo if you have one. Don't worry, you can change this all later. If you're not ready to fill it in, you can skip it, too.
When that's done you'll see that you are following an account. That account is the staff Tumblr. (You can remove Staff if you want to.) Entries from this Tumblr will be displayed in your dashboard.
When you add more friends, their Tumblrs will appear here, too.
So! You've started an account and started tumbling. New York Times writer Paul Boutin timed how long it took him to sign up. He clocked 35 seconds. That's at least a minute faster than it took you to read this post!