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.
You can find worksheets for a wide range of courses--almost any course you want to teach your children. These include spelling, writing, English, history, math, music, geography, and others.
I recommend getting one of these books when you first begin homeschooling and use it as a reference throughout your homeschool journey. Regardless of how long you homeschool, you'll always have doubts and questions about how your child is performing.A scope and sequence book can put your mind at ease.
However for the most part, when a worksheet is needed to help drill down a procedure, standard, or lesson, its effectiveness can and will vary.