Ask the students to write down the decimal.
Tell the students to separate each number after the decimal with a few spaces. For example, if the number is 4.383, they should write it as "4. 3 8 3."
Show the students how to make a fraction out of each of the spaced-out numbers. The first decimal place is divided by 10, the next place is divided by 100 and the next place is divided by 1,000. Show them that the trend is to add a "0" to the denominator to make the next decimal place a fraction. In this case, the number becomes "4. (3/10) (8/100) (3/1000)."
Show the students that they can put all of the decimals back together, and use the last denominator to create the entire fraction. In this case, the fraction form is "4 and 383/1,000."