Most older engines, and many newer ones, have timing marks in the form of a line marked on the rim of the vibration damper.
Some engines in front-wheel drive vehicles have timing marks on the flywheel. A pointer is attached to the timing cover.
When the mark is exactly under the pointer, the engine is ready to fire number one cylinder.
The spark will occur with the rotor pointing to the number one cap terminal.
The timing is generally set by using a strobe tamp, which is a light that is operated by high voltage surges from the spark plug wire.
The strobe lamp usually referred to simply as a timing light.
A useful timing strobe can be constructed using 9 high-brightness LEDs and a few common components: 2 monostable (CD4098), 1 double operation amplifier (CA3240E)
and 3 transistors.
Ignition pulses from the number 1 cylinder high-tension lead are used to trigger the circuit via a home-made inductive pickup.