Make sure to drop you wrists similars to what you would do on a topspin FH. Also, you want to keep your arms and upper body loose to generate maximum racket head speak. And like others have mentioned the grip is important. Generating topspin on the BH is very helpful. It allows you to get the ball high and deep, pull opponents of the court with safe angles and it let's you create sharp angles and bring to ball up and down quickly on passing shots.
Please excuse my punctuation and grammar.