These tips are good for any online information posting, regardless of the website.
Is It Too Much?
It is okay to put "18 years old", but 04/22/85 is way too much information. Although the normal uses of these websites are fun ways to meet people, too much information makes it way to easy to attract unwanted people. Not everyone who has a .edu email address is a student! Don't put a phone number, but put an area code if you want others to know your region. By combining things like Google, ulm.edu, AnyWho, etc., with certain information a person can get a map to your door!
If one computer can see it, all computers can see it. Unless encrypted or otherwise secured, nothing is private on the web!
Putting your major may be okay, but never your class schedule.
If someone threatens you online, save the conversation and then report it to the police. 1.4 million men and women are stalked annually. The internet opens that situation up to the entire world. It is possible to be stalked from anywhere, and then the perpetrator is given everything he/she needs to come to you.
Computer harrassment and cyber stalking is a crime and should be reported immediately to the University Police.
Eggs in a Basket
Though it may be easier to remember, you should never use your CWID and password for other accounts, including Facebook, eBay, Paypal, and other online sites. If one of these service providers were to be compromised an attacker could access all of your accounts. Worse yet, an attacker would have access to your email, which many online service providers use to verify your identity when changing passwords. In essence you could end up locked out of your own accounts.