If possible, stay employed while job hunting. Although it's more important to be employable than employed, there is still a positive bias toward someone currently employed. Although this bias can seem irrational, it's human nature to want what's in demand. That's why people tend to flock to the most popular movies, buy the books on the best-seller rack at the bookstore, and to look twice at merchandise they've seen others use or wear.
By contrast, if you seem needy and easy to get, people will be less eager to hire you and more reluctant to make a handsome salary offer. As James Crowe, CEO of Level 3 Communications, says, "We want people who are in demand. They generally have to walk away from money. Then we will do what is appropriate [to get them]." Having a current job while you search for your next job enhances your personal brand as a person who is in demand.