What is the best way to acquire voltage information of a battery powered microcontroller project?
The voltage divider you mention is the easiest way but it doesn't mean it's the appropriate. however, if you want to go for it, to reduce the current the resistors draw, use large values (Ohm's law, I=V/R), just make sure the relation of both resistors complies to your ADC resolution vs the battery voltage.

There is also Battery Chargers IC that provide extensive telemetry of battery via I2C. Check for instance LTC4162. 

If you provide more info about what you want to do, such a battery capacity, uC used etc, maybe you can get a better answer