Determine if the entire fraction has a negative exponent. For example, (3/4)^-5 has a negative exponent for the whole expression, but (3^-2)/(4^2)^2 has a negative exponent only within the expression.
Flip the whole fraction, if necessary. This step is only necessary if the answer in Step 1 is "yes." If you flip, change the sign on the outside exponent. For example, in (3/4)^-5, flip 3/4 to 4/3 and change the -5 to 5. The term becomes (4/3)^5.
Re-express any terms within the numerator that have negative exponents by substituting 1 in the numerator and the rest of the term in the denominator. For example, if your original expression is 2^-3/3^4, you need to re-express 2^-3. Write it as 1/2^3 and substitute that in the whole expression, getting 1/2^3*3^4.
Re-express any terms within the denominator that have negative exponents. For example, if your original expression is 3^3/2^-2, re-express the denominator as 1/2^2. Then write the denominator of this part in the numerator, and 1 in the denominator, getting 3^3*2^2/1 or just 3^3*2^2.