What makes a measurement more precise than another?

1) Use of instruments with smallest precision
E.g Micrometer (0.01mm) is more accurate than Vernier
Caliper (0.01cm)

2) Correct eye position
To eliminate parallax error

3) Reduce human error by dividing the time taken by the
number of oscillations.
E.g 20 oscillations timing is 18 seconds. Human reaction
error is about 0.03 seconds. Dividing 18 seconds by 20
oscillations to get the time taken for 1 oscillations will
reduce human reaction time by 20 times. I think this is
called percentage error. Same thing goes for the
measurement for the diameter of wire by winding it
around a core 20 times and measure.

4) Take average measurements to increase accuracy.

Etc... If u need more, u can comment.