When talking about your hobbies, mention those you do in or as part of a team, first; and talk very briefly about each. What got you into it; How you go about it; How you contribute and/or perform, etc. Engineers work in teams, so mentioning those and showing your keen interest in them gives you a plus - Team Spirit. Very necessary.
When asked about your weaknesses, say just one or two 'not-so-negatives' and quickly talk about how you're working to overcome them or suppress their effects. If, rather than one probing question after the other, you're given the much-dreaded (at least in my case) "Describe Yourself", you should remember to talk about weaknesses too, in the same manner I mentioned earlier. Among other advantages, it shows maturity, honesty, humility and hard work.
What do you have on your skill-set or extras list? Do you code (and I don't mean proficiency on the level of some top Software Engineer whose name just popped up in your mind as you read that, but, at least, do you?)? How well can you use AutoCAD [Electrical], Microsoft Visio, Simulation software such as Multisim; etc etc? Whatever they are, polish-up your knowledge and be ready to defend them in the interview room, and subsequently, throughout your internship period.