Personality Questionnaire Tip 1: Get to the assessment centre early
You will behave most like your usual self, and answer most honestly, when you are calm and focused on the questionnaire in front of you. If you have just rushed through the door and are worrying about putting on your name badge, you are unlikely to show yourself in the most accurate light.
The personality questionnaire itself will unlikely be timed, however this does not mean you can spend all day considering your responses. The instructions for the test will probably tell you to answer quickly because the first answer that comes to mind is usually the one most reflective of your true feelings.
Personality Questionnaire Tip 2: Answer honestly but with the company and position in mind
It is very difficult to distort the results of a psychometric personality questionnaire, however if you research what sort of person the company is looking for, you might be more likely to answer with that company's values in mind. Companies often list the competencies they are looking for in each role. It's worth reminding yourself of these before you take your personality questionnaire. Don't consciously try to answer how you think they want you to answer though as you are likely to get it wrong and if you're not answering honestly your answers will appear disjointed in the results.
Your first answer is probably the most accurate reflection of how you feel about a question.
The other thing to bear in mind is that the personality questionnaire instructions will usually tell you to answer in the context of work, not your social life.
Personality Questionnaire Tip 3: Don't sit on the fence
Try not to answer too many questions with the response "Neither Agree nor Disagree" otherwise you will be in danger of appearing to be indecisive or lacking conviction. It also makes it difficult for the test administrator to establish what you're really like and if they don't get a strong positive match to a role, they may put your application in the 'no' pile.
Personality Questionnaire Tip 4: Don't be a drama queen
Conversely to the previous tip, you should also avoid answering every question with "Strongly Agree" or "Strongly Disagree". This might make you appear wildly sure of yourself or closed to others' opinions. The questions will usually include some extreme statements to which not answering strongly agree or strongly disagree will be your natural response anyway.
Personality Questionnaire Tip 5: Be consistent
Personality questionnaires deliberately ask the same question more than once but phrased slightly differently. They do this not necessarily to check if you are answering truthfully, but more to measure just how strongly you feel about something. For example, if you really feel strongly about being honest, you will always answer "strongly agree" no matter how the question is phrased, but if you think that in some situations honesty isn't the best policy, you will moderate your responses. This will show up a scale in you results.
The personality questionnaire report seen by the employer will show how consistent you have been in your responses. If it shows that you're trying to manipulate your responses this won't be viewed favourably by the employer.
Personality Questionnaire Tip 6: Answer in a work context
You will be told this before you start your personality questionnaire but it is important to bear in mind, especially when you find yourself thinking "it depends" for an answer. The employer is interested in only how you might perform at work, so try to keep your responses in keeping with your work personality. This approach will also help you imagine yourself in the scenarios presented and decide on your response.