potentiometer placement in LED circuit

I'm building an LED circuit for a model application and I want brightness control via 2K ohm potentiometer. Should this potentiometer be placed in the the circuit before or after the current limiting resistor(s). Also, Should each LED have its own resistor or is it suffucient to have resistors on the entire circuit? 

The circuit will involve a 12v 1A power supply and 5 LED's drawing 2.2V and 25mA each. 

I have another circuit which involves 12 V LED strip. I would like to have intensity control for this circuit as well. 

Thanks!

What you have be aware of is the brightness is proportional to current, so the design has to take that into account.
2.2 V Vf is nominal, there is a spread on it, it is temperature dependent, an it changes non linearly with current, so you have to look at that as part of the design process.
Where a pot is in a series circuit is immaterial.
If you have a series LED string, then only one resistor, if parallel, then one for each.
A series string is marginal in that you are close to 12V for the sum of the LED forward voltages, and if parallel, you are throwing away a lot of power in the resistors.
PWM or a voltage controlled current source will both give better control of brightness(VCCS will be marginal with a series string, voltage compliance will be a problem)
Cheers,
Richard