Step 1 : Make a new character of the race / gender / appearance you want to be, class does not matter. Also, for example if you're a tauren druid, you can be ANY race you want not just a night elf.

Step 2 : Log onto the newly made character, and then log off.

Step 3 : On the character selection screen, have the character you want changed “ Highlighted ” in that they are the character is shown enlarged, and have your cursor over the level 1 you want to look like. Click that level 1 and press enter at virtually the same exact time ( but with the clicking part being slightly before). If you fail in doing so repeat step 2 and try again.