There are several standard exercises which train students to convert percentages, decimals and fractions. Converting percentage to decimals for example is actually as simple as moving the decimal point two places to the left and losing the percent sign "%." Thus 89% is equal to 0.89. Expressed in fraction, that would be 89/100. When you drill kids to do this often enough, they learn to do conversion almost instinctively.
Hopefully this has inspired you to develop exciting and engaging review worksheets for your class when needed and your students achieve as much as they can when it comes time to test.
They're also available for nearly all grade levels. There are printable middle school, high school, elementary school, and even pre-school worksheets.
Review subtraction of 2 numbers whose sums would be 18 or less