While there is no definitive answer to this question, in my opinion, few of the desirable characteristics an engineer should possess are - 1. Practical (hands-on) and analytical approach 2. Mastery on engineering fundamentals learnt in engineering schools and colleges 3. Mastery on engineering drawing (fundamentals, regardless of a particular discipline) The list can be exhaustive. These are some points which came to my mind on an impromptu level. The crux is to never deter from the basic engineering principles.