Any hitting help? All comments appreciated!?

I have been a libero for a few years. I got moved up to varsity last year and did some hitting on the side but libero has always been my key position. I played club volleyball this past club season as an outside hitter and did a pretty decent job. Now, my coach switched me to an outside hitter for the upcoming high school regular season and I really want to take it seriously and do a great job. I'm pretty short, but I have a decent jump and a pretty quick approach. I manage to get the ball down pretty well and I can hit hard but I only hit hard by accident (lol!). I haven't figured out completely what makes me hit hard so I can do it every time. What do you do to make a volleyball hit harder? Also, I can hit pretty well anywhere except for the left corner when I hit. I always hit across the court, but never straight down the line. I know I can do it, but when I try I never do. Also, I'm right handed, but I want to learn how to hit with my left hand, too, because my setter sometimes hits WAAAAY too far outside and I can just barely reach. I can hit left handed but it's always a very soft hit and I have no control of the direction. And, any tips for blocking?