Some general weaknesses
It's important that you understand what your weaknesses are. You will be questioned during the interview about anything unclear in your CV and should be prepared for such questions. Balance your weaknesses with achievements.
If there is a clear lack of balance between the job requirements and your skills and experience, you will not be offered the job. One should then investigate how to bridge the gap. If education is an issue then a course or formal qualification could help you compete with the other candidates.
Make sure that you have common weaknesses or, even better, turn your weaknesses into strengths.
For example:
Have a friend or yourself look at weaknesses in your career through your CV. Which points would potential employers be likely to question you about?
Once you prepare answers to common questions you're able to start tackling the more difficult parts of your interview and tune your CV accordingly.