I grew up in Australia, and learned that when I write a check, I should generally cross it with two diagonal lines with Not Negotiable written between them. The idea being that this signifies that the check can only be deposited into an account owned by the named person.
I read, obliquely, in this question on this site that a similar thing can be done in the United States by saying For Deposit Only.
Do two diagonal lines mean the same thing on an check in the United States?
For those who think this is urban legend see this link on the National Australia Bank website.
Effect of crossing
If you cross a cheque (by drawing two parallel lines from top to bottom across the front of the cheque), you are telling NAB not to cash it over the counter. The cheque therefore must be paid to a bank (e.g. into a customer's account). If NAB does cash a crossed cheque, it may be liable for any loss suffered by the true owner.
Meaning of 'not negotiable'
You may write the words 'not negotiable' between the two parallel lines on your cheque. This means that if the cheque is transferred to another person, the person who obtains the cheque has no greater rights to it than the person who gave it.
For example, if the cheque was stolen, the person from whom the cheque was stolen might recover the amount of the cheque from the person who received payment, even though that person who received it may have done nothing wrong.