Just google 'scrabble strategy' and memorize all the 2 and 3 letter words, that will easily take you to the next level. There are a bunch of weird ones that are good to know: aa, ae, ai, qi, ki, za, ba, bo, bi, li, om, em, ef, er, aw, xu, xi, etc.
You don't need to memorize the definitions though it's easier to if you see a list with the words and the definitions. Aa is a form of cindery lava, an ai is a type of sloth, a xu is a form of vietnamese currency, etc.