It's easy. Choose what you are testing. Ohm's (resistance), DC voltage, AC Voltage, Current (amps or milliamps). Choose which range, remember most vehicles are 12 VDC (actually closer to 15 VDC), so just choose a range higher than that. For Ohms, choose a higher range, see what the resistance is and lower the range to match. A short will give full needle sweep, an open will give no needle movement. Resistance will be somewhere in between. The higher the resistance, the less needle movement you will get. The most accurate readings will be the one that puts the needle somewhere near mid scale.