For your weaknesses, be honest about them but be sure to emphasise that you learned something from them (and try to explain how you learned from them or how they made you a better person).If you have a readily apparent weakness, discuss how you've addressed it and why it won't be an issue in the job. Here you can discuss non-essential skills also. For example you say like:

☛ Being organized wasn't my strongest point, but I implemented a time management system that really helped my organization skills.

☛ I care too much about my work.

☛ I am too much of a perfectionist.