Know the difference between tenths, hundredths, thousandths, etc. For example, in 25.783, the number directly to the right of the decimal (7) is in the tenths position. The number to the right of the 7, (8), is in the hundredths position. The number to the right of the 8, (3), is in the thousandths position.
Look to the number that is farthest right of the decimal point. For 25.783, look at the 3, because it's the farthest number to the right.
Go by the rule that if the number to the right of what you are rounding is 5 or larger, increase the number you are rounding by one digit. If the number to the right of what you are rounding is 4 or smaller, the number you are rounding stays the same. After you round, every number to the right of the number you are rounding disappears from the end number.
Try the method in Step 3 by rounding to the nearest hundredth position for 25.783. The digit in the hundredth position is 8. Look to the right to find 3, which is smaller than 5, so the number 8 does not change. The rest of the number disappears. The end result is 25.78. However, for 25.789, the number to the right of 8 is 9, which is larger than 5, so the number 8 increases by one digit and the rest of the number drops off. The end result is 25.79.