If you have a Site Meter, you'll notice on the "Summary" page a list of links for additional information. This is on the left of the screen. Under "Recent Visitors" you'll see "By Details" and then under this "By Referrals". If you click on the "By Referrals" option, it takes you to a list of the referring sites of the last fifty visitors to you site.
The first thing you'll notice is that there are a handful of "unknowns" on the list. That means that the person did not use a link on a web page to get to your site, but instead used a bookmarker or typed your address in the long way. If you scan the list again you'll notice a lot of "http://www.deardiary.org/cgi-bin/viewer.cgi"; these folks probably got to your diary by using the "Show Diaries Recently Updated" option on Dear Diary's home page. Other links are from people's email pages, where they used the link from the "notify" they received for a recent update you made.
But if you're interested in how the search engines are finding you, look for entries that start with things like "http://www.google.com/search?" or "http://search.yahoo.com/search?" or "http://search.iwon.com/" or "http://search.aol.com". There are innumerable search engines out there, but most of them will have the word "search" embedded in the URL of the search they generate. If you click on any of these search links, you will see the page that was generated by doing the search, and that page will show you the key words. They key words are also embedded within the search URL itself, but if you lack experience reading URL's you don't need to worry about finding the key words that way.
While the "turtle tank" interest seems to be finally dying off, I note with interest today that I'm getting a persistent repeat hits on searches using "kitten + shots" and "snake + dreams". I've also had one very persistent inquiry concerning "aura + quiz"; this person has looked at my diary page for nearly every day in the last week using that search. The weirdest current search hit by far is "cracked hero dvd player user-id". I cannot begin to imagine what that person was looking for, but it scares me a little.