How to amplify an electret microphone
Ok this will be quick and hopefully painless. 



I am not well versed in the microphones themselves, sometimes they are biased sometimes they are not. 

So the way this is designed:

Remove DC bias from microphone output

Bias the transistor so that it can maximize the usable range

(For simplicity make R1= R2 10k resistors or less should do it)

Rg (plus the beta of the amplifier) control the gain of the circuit. The higher Rg the higher the gain. HOWEVER, the larger Rg gets the more power it dissipates. this is for low current systems. 

the transistor is an NPN (always open, apply voltage to close) 

This is also an INVERTING amplifier. For audio applications you will not hear the difference; however, if you use it for anything else it applies a negative gain. 

(Vout= -Gain*vin)