Here is another strategy.
Each 2 needs a 5 to make 10 because a terminating decimal can be written as a fraction whose denominator is a power of 10.
Multiply both numerator and denominator by 5*5*5 which equals 125.
Move the decimal point two places to the right to get 12.5%
You can do what Kevin W. suggested; divide 1 by 8 and divide until the division stops or terminates. After that, as Kevin W. said, multiply by 100 or move the decimal point two places to the right and add the % symbol.
When dividing make sure that the numerator is on the inside of the division sign and the denominator is on the outside of the division sign.
8l 1.000 Add zeroes as you divide until the division process stops. I added three zeroes because I knew the division process would stop after three divisions because of the three 2's.(1000 is the smallest power of 10 divisible by 8)