There are three types of taxis you can use in Mumbai.

(1) Black & Yellow B&Y { non-air-conditioned } The old non AC taxis are being phased out by the Government.replaced by the newer non AC ones All of them have an electronic meter on the dashboard which shows the exact amount of money you need to pay the driveron completion of the ride.  Always ask the driver to go by meter before you get in. Ensure the meter is set to INR 19/- as the base fare before the starting of the taxi .

(2) Blue & Silver B&S {air-conditioned}. AC taxis cost 25%more than the B&Y non-AC ones.Thr base fare and corresponding per km & waiting hours charges.

(3) Radio Taxis. These are on-call taxis (AC) which can be ordered over the phone/internet to com for a pickup at any particular spot at no extra charge.currently You can login online and book them months in advance after choosing your location. The best radio taxis are:

 

Mega Cabs 

Meru Cabs 

Tab Cabs 

Easy Cabs 

Clear Car Rental 

Carjee.com

 

All the three taxis mentioned above have electronic meters and it is compulsory for the driver to put them to use.  

All taxi meters and fares are in INR, even if asked for USD, pay only in INR.

There is another very easy and best way to roam the major cities in India - Hire a car for the full day (It comes along with driver and petrol)