Precision describes measurement resolution and agreement among repeats; accuracy describes closeness to an accepted value. A balance can repeatedly show 2.50 g for a 2.70 g standard: precise but inaccurate.
Choose suitable range and smallest graduation. Read the bottom of a concave meniscus at eye level to reduce parallax. Record an exact microscope setting such as 400×, not “high”.
Digits must match the instrument. On an analogue scale, make only a reasonable intermediate estimate between graduations; do not invent unsupported decimal places. For 4.32 g, 4.28 g and 4.30 g, the mean is 4.30 g. Writing 4 g discards information; writing 4.300000 g invents precision.
A digital microscope, video, data logger or simulation can extend observation, but calibration, sampling rate, sensor resolution and model assumptions still matter. More decimal places cannot replace an adequate sample size.