You did not tell us if you are talking about a digital or an analog multimeter.
The digital ones are getting quite common nowadays but here's another no no for analog meters: do not reverse the probes to get the pointer to slam the wrong way - it does not like that :cry:
To check your meter just test something you know, for example, a new good 9V battery has about 9.6V, if your meter reads way different its faulty.
Do the same with a known resistor in the Ohm range. If both these measurements were good you can check the current range with the battery , the resistor and the meter in series. You have to use Ohm's law to calculate the expected current first.
If voltage and Ohm work but no current then its likely the fuse in the meter has gone, replace it after confirming with the ohm range it is indeed open circuit. Use only an exact replacement fuse - it is there to protect your meter.
Digital meters either work correctly or not at all in my experience. Only in the Ohm range you may get funny readings if your probes have a poor connection somewhere, that is easily checked by shorting them (0 ohm reading or very close to it).
Klaus