The Facebook usernames will have to be at least five characters in length and can only contain letters, numbers, and a period. Trying names with special characters -- you know, symbols like $#@% -- will only waste your time.

6. If you created your Facebook account after 3 p.m. on June 9, you won't be able to get a username yet.

Facebook is only letting users who had accounts prior to 3 p.m. on June 9 register for usernames this week. The social network says it's a precaution to help prevent people from creating accounts just for "name squatting" purposes. If you registered your Facebook account after that time, you'll have to wait till June 28 at 12:01 a.m. to get your new name.

7. The restrictions are even greater for Facebook Pages (public profiles).

Owners of -- public profiles for companies, organizations, or public figures -- must have been registered before May 31 in order to be eligible for a custom URL. Additionally, the Facebook Page must have had at least 1,000 fans as of May 31 in order to get a username now.