I'm not sure what category it'd go in.
The title right now is How do I track people who visit my journal? How do I add a counter to my journal? Let me know if you want that changed.
LiveJournal does not currently offer a tracking or counter service to its users. Additionally, there is no way to see the usernames or names of people who visit your journal. LiveJournal does provide a mechanism to track the IP addresses of people who comment in your journal. This is explained in more detail at http://www.livejournal.com/support/faqbrowse.bml?faqid=66.
If you use S1 (http://www.livejournal.com/support/faqbrowse.bml?faqid=173), you can add a third-party counter to your journal's style. This will allow you to count the number of people who visit your journal, and, depending on the counter service that you use, it may provide some information about the people visiting your journal. The "HowTo" journal (http://www.livejournal.com/userinfo.bml?user=howto) contains a tutorial which explains how to add a counter if you use S1. You can read it at http://www.livejournal.com/users/howto/1332.html.
Users with Free Accounts who use S2 cannot add counters to their journal styles. Users with Paid, Permanent, or Early Adopter accounts who are using S2 can add counters in custom S2 styles, which is explained at http://www.livejournal.com/support/faqbrowse.bml?faqid=177.
Alternatively, any LiveJournal user can add a counter to their journal by placing it in a backdated entry (http://www.livejournal.com/support/faqbrowse.bml?faqid=91) that has a date far in the future.
If you are concerned that unwanted people are reading your journal, you can use security settings (http://www.livejournal.com/support/faqbrowse.bml?faqid=24) to determine who can read your entries.