1) Find people's tumblogs you like and click "follow" at the top right. Then your Dashboard will present their posts in chronological order. When you see a post you like, click the little heart; the person will get a notification you liked it. You can also click "reply" and type a short text message if you please. Thus, you build social cohesion.
In
http://www.tumblr.com/customize/nervouspete:
2) click Advanced and change "posts per page" to some number you are comfortable with
3) tick "enable high-res photos" to get an automatic lightbox
4) tick "use descriptive URLs" and when you write a post you can edit the slug (the text part of the web address)
5) tick "promote tumblr" to encourage people to follow you
6) you can add "Pages" which are static content -- like where you'd write a little bit about yourself. Most Tumblr themes will put permanent links to Pages somewhere in the navigation.
7) there are a wide variety of custom themes for sale, from $9-$49. Some of them are very nice and they do help your blog stand out, so they can be worth looking at. There are cheaper options too; for a round, see
http://onefps.net/post/7772700226/premi ... heme-shops(Bonus thing not related to photography but you'll like it: check out
The Otlet's Shelf theme.)
Finally, let me know when you're ready, and I'll "reblog" one of your pictures. This means the picture will appear (still accredited to you) for all my followers to see, and I'll mention who you are and that they should be following you because you take awesome pictures.