Recruiters tend to use these tests as indicators only, rather than a deciding factor. Psych tests can be affected by how you feel right at that time, and they are not 100% reliable. There are increasing levels of sophistication that cross check a respondents answers to help identify whether he/she is being truthful.
As mentioned, books on psych tests and assessment centres will explain the thinking behind such tests and give some general advice on how to conduct yourself.
Having done some and also having administered some, I would say there's little point in trying to answer in an unnatural way. It's probably worse for the test to indicate that you're lying or being inconsistent, rather than it indicate aspects of your personality which are close to the truth.
Recruiters are fully aware and accepting that everyone has character flaws, and that these can be overcome or outweighed by character strengths, or a good level of self-awareness and determined action.
A smart candidate will have tried some of these tests, looked at the answers and thought about themselves in order to better present themselves in an interview e.g. "I know that one of my failings is that I do too many hours at work, and have sometimes become stressed out. Knowing this, I set cut off points and stick to them, and do a lot of exercise to manage any stress. I ringfence family time and nothing gets in the way.".