yeah reading is the best way, you can try listening to songs and shows too, sometimes they use words that are not commonly used in daily life. but for reading, start off with short articles/stories first then go on to books. it can be stories, non-fiction, anything that interests you.
the other way, flip through the dictionary. you can start from A to Z but thats REALLY boring. or else, do random flips. open the dictionary and find out the meaning of any word that catches your eye. whichever, overtime you'll improve =]