A customs officer is more of an assertive communicator than a legal enforcement officer or police man. A strong sense of honesty and unfettered faith on law are important. A thorough understanding of customs rules and understanding of permitted and non-permitted goods is important. Good judgement of situations, fast decision making, assertive communication, ability to question people, being unbiased, attention to detail, ability to work alone, ability to take orders, being able to work alone & as part of a team, etc are skills essential for surviving in this line of work. Honesty, fearlessness, good judgement skills, etc are also imperative skills. You will be working during odd hours of the night, braving unsocial conditions.