How do I measure the current flow to a component?
Honestly, People often use a simple sense resistor. 

You place an in series very low resistance resistor(&lt;1 ohm often) and you measure voltage drop. This allows you to monitor motor current.

There are many many motor control algorithms if you want to control the motor yourself, otherwise, if you are measuring for just knowing current draw, you just need to make sure you sample often enough to get an accurate measurement, or use a circuit with a lowpass filter effect(make sure you buffer the voltage).