To do significant figures correctly, follow these main rules:

1. All nonzero digits are significant.
2. Zeros between nonzero digits are significant.
3. Leading zeros (zeros to the left of the first nonzero digit) are not significant; they only indicate the position of the decimal point.
4. Trailing zeros to the right of a decimal point are significant.
5. Trailing zeros in a whole number without a decimal point are not significant.
6. Exact numbers (like 1 meter = 100 centimeters) have an infinite number of significant figures.
7. When doing calculations:
   • For addition and subtraction, the result should have the same number of decimal places as the number with the fewest decimal places.
   • For multiplication and division, the result should have the same number of significant figures as the number with the fewest significant figures.
8. When rounding, if the digit after the last significant figure is 5 or more, round up; if it is 4 or less, keep the last significant figure as is.

Example:

• The number 0.00452 has three significant figures (4, 5, and 2).
• The number 4500 can have two, three, or four significant figures depending on how it is written (4.5 × 10^3 has two significant figures, 4.50 × 10^3 has three, and 4.500 × 10^3 has four).

These rules govern how to identify and work with significant figures in measurements and calculations to reflect the precision of the values accurately.