Use mnemonics and silly stories to help you remember. A mnemonic is a special technique or learning device that helps you remember something. Stories like Times Tales can help you memorize your multiplication facts by associating the numbers with silly characters and stories. Phrases like 5 6 7 8, 56 equals 7 times 8 are also useful. There are many ways to memorize things, you just need to find the way that works best for you.
In the simplest cases, the two fractions will already have a common denominator. In this case, add the numerators and then reduce the resulting fraction.