Convert Fractions to Percents
Divide the top of the fraction by the bottom, multiply by 100 and add a "%" sign.
The simplest method is to use a calculator:
Steps:

Example: What is \frac{5}{8} as a percent?
Get your calculator and type in "5 ÷ 8 =", the calculator should show 0.625, then multiply by 100 and your answer is: 62.5% (remember to put the "%" so people know it is "per 100")
Of course you can do the division in your head or on paper if you don't have a calculator.
Another Method
Percent means "per 100", so try to change the fraction to \frac{?}{100} form.Follow these steps:
Step 1: Find a number you can multiply the bottom of the fraction by to get 100. 
Step 2: Multiply both top and bottom of the fraction by that number. 
Step 3. Then write down just the top number with the "%" sign. 
Example 1: Convert \frac{3}{4} to a Percent
Step 1: We can multiply 4 by 25 to become 100
(why 25? because 100 divided by 4 is 25)
Step 2: Multiply top and bottom by 25:
×25  
\frac{3}{4}  =  \frac{75}{100} 
×25 
Step 3: Write down 75 with the percent sign:
Answer = 75%
Example 2: Convert \frac{3}{16} to a Percent
Step 1: We have to multiply 16 by 6.25 to become 100
(why 6.25? because 100 divided by 16 is 6.25)
Step 2: Multiply top and bottom by 6.25:
×6.25  
\frac{3}{16}  =  \frac{18.75}{100} 
×6.25 
Step 3: Write down 18.75 with the percentage sign:
Answer = 18.75%
Yet Another Method
Because a percent is actually a ratio (parts per 100) we can also use Proportions to do the conversion.
First, put what you know into this form:
\frac{Top of Fraction}{Bottom of Fraction} = \frac{Percent}{100}
Then solve using "multiply across the known corners, divide by the third number":
Example: Convert \frac{3}{16} to percent
Fill in what you know:
\frac{3}{16} = \frac{Percent}{100}
Multiply across the known corners, then divide by the third number. The "known corners" are top left and bottom right:
Percent = (3 × 100) / 16
= 300 / 16
= 18.75%
Answer: \frac{3}{16} is 18.75% (same answer as the previous example!)