The most effective strategy to answering an interview "weakness" question is to offer a genuine response, but one that is strategic and ultimately positive in selling a person's abilities. For an office manager role, a person may note difficulty in public speaking, for instance.
A person should avoid using the word "weakness" in the response. Also, it is ideal to talk about growth and development to leave the response on a positive note. A person might say that she hasn't always been confident in public speaking but that she joined Toastmaster's because she wanted to improve. While public speaking isn't typically relevant to an office manager role, this response shows genuine desire to grow and a willingness to learn.
Asking a prospective employee to describe his weakness is a typical interview question used to find out if the employee has a flaw that might be pertinent to the job. The best policy is to turn this question on its head and discuss something unrelated to the job or something easily construed as positive. Do not use the word weakness back at the interviewer when describing the non-essential skill or characteristic.
An example of a non-essential skill is to say you struggle with group presentations in a job that is unlikely to consider that essential. A characteristic weakness might be considering yourself a perfectionist and taking a long time on projects because of your need to get everything just right. The other option is discussing an improved skill, but make sure that it is not a skill related to the job you applied for. Instead, choose something you were weak at in your last job, but improved during the time you were there.