If you receive a verbal job offer that you decide to accept wait until it is in writing before resigning from your current employer.
Factors to think about before accepting an offer of employment:
Am I happy with the money and benefits that have been offered?
Am I happy with the commute to work each day?
Will I fit into the company culture?
Where will this job situate me career wise in two-three years time?
What do my instincts tell me?