☛ Strengths are skills or values you feel are an asset. Rather than just listing these down, be more specific. Values are relative, therefore tricky. You can be patient, but patient to what extent and in what context? Are you able to endure instructing someone who can't seem to understand you, or are you uncomplaining of people who are late? You can also give brief examples to be better understood.

☛ Weaknesses are skills or values you feel can be a liability and need to improve on. Since these may seem like points against you, turn the negative into a positive. Give weaknesses that, when looking on the bright side, can also be a strength, and highlight that fact. You can also give a weakness that you've created alternative solutions to or are currently working to correct. This article on About.com has some great suggestions and examples.

Never refuse to answer these questions or give vague and non-committal answers since this will give the impression that you either do not know yourself well or are not confident enough in your abilities to recognize what you're best at and what you need to work on.