A lot of people are curious about their IQ. This is only normal. Who would not want to know how “smart” he is? The thing about IQ tests is that there are so many that are available. This can make choosing particularly hard. One of the tests that people are raving about is the MENSA test that is available online. Do remember that the results of the IQ test do not define how smart you truly are.
You should remember that there are some people who are book-smart and there are also some people who are wise. Those who are wise are able to do things in life that others would not think of. You can use the results of the IQ test in order to become inspired to improve yourself further.
This is a minefield question if you mean which of the available tests for psychologists to use. However, since at least three aspects of intellectual functioning: memory, verbal reasoning, non-verbal reasoning (spatial ability) are necessary for an IQ to be calculated, the Wechsler Scales which include a number of sub-tests tapping these areas, are the most likely to return a valid and reliable result.
When a psychologist administers a standardised test individually there are clues in the way a person approaches the tasks which enhance the results gained from the set calculations. The time allowed for each task and the manner of presenting it is set down very precisely so that the results gained for an individual on one occasion with one psychologist should be virtually identical with those gained on a second occasion even with a different psychologist. Basically, if you are thinking of trying a free test on-line then don't take too much, seriously. It will be a very blunt instrument.