Take your LJ username and replace each letter with the corresponding number (A=1, B=2, etc...).
1 4 13 9 18 1 12 13 5 13 15
Add all of the numbers together to create a kind of super number.
Make a note of the first digit of this number, then add the digits of the number together.
Find the post of this number in your LJ. If you don't have that many posts, add the digits together again. Keep doing so until the number is smaller than your pathetic number of posts.
My fifth post
Take the digit you noted in step 3, and count that many words into the post.
Word #1 = "First" (Wow... :-P)
Use the resulting word in a Google Image Search, and select a picture from the first page.
Apparently, it's the first flight of some sort of aircraft or rocket. Looks cool.