Grind size - Fine (Aeropress or pressurized portafilter or commercial espresso grind size will do)
Moka pots are size specific. the funnel needs to be filled to the brim with coffee grounds. Can’t make half the capacity in it.
On the topic of filling - leave a 1-2mm clearance from top in the funnel. do not tamp, just level evenly with light pressure of fingers. This is important because the grinds swell up when hot water passes up through them - if too tightly packed, the pot will either leak or worst, push the finer grinds through into the brew chamber.
Use boiling hot water to fill up the lower pot - this is to reduce flame exposure time to the pot. Note: Make sure that the water level is just below the steam escape valve. If you exceed this level, the pot could leak hot water or worse - the water will go up the funnel and wet the bottom portion of your coffee grinds - resulting in uneven extraction.
Once ready, place the pot on slowest burner at lowest flame settings - flames could not come out from the sides - this is important. If you only have bigger flame rings or have an induction, use a flat pan and keep the Moka pot on it.
Stay around - As soon as you start hearing the gurgling sound, lift up the lid briefly to check the brewed coffee levels. Once satisfied that only steam is coming out from the chamber below or it starts sputtering, lift the pot immediately from flame and take it to the sink and cool bottom chamber with tap water.
Measurements - A two cup Bialetti Moka pot will hold exactly 100ml of water till the pressure relief valve in bottom chamber. The funnel holds 11-12gms of coffee grounds, resulting in 75-80ml of brewed coffee.
Cleaning - the most overlooked part of Moka pot ownership. Lift the white rubber washer from bottom of upper chamber, remove the mesh filter and clean the insides with soapy water from time to time. Not cleaning this part is no.1 reason for stale tasting coffee.
To know more about Moka Pot brewing check out our Moka Pot Page