Try hitting a bag on a post or pole. make sure the bag is padded enough that you bat is safe. stand at a correct distance and hit the bag as if you were swinging at the ball. Use a heavier bat. make sure everytime that your hips are turning hard and the barrel of the bat is hitting over the plate in the spot where the ball would be. maybe shorten your step with the lead foot or not step at all if you want speed. this will strengthen your arms to gain quicken and get the head of your bat around. Swing hard and have fun.

Coach Jones

It is important to use your hips on giving power to your swing. improve you core muscles, do more rotational core training to improve on bat speed.

http://www.softballperformance.com/softball-hitting-drill-to-increase-bat-speed/

put in extra weight to your bat and swing as hard and as fast as you can. Never do it right before you get up to bat. But just do dry cuts of this. It will make you stronger.