If you're wanting to give a free trial, but wondering if it's the best option, this is the post for you. Free trials are a great way to get your app on the home screen but you still have to give value when the free trial ends, assuming the user doesn't purchase.
The important thing is that you're giving the user all the features for a period of time. You want to show off everything they will miss when the trial runs out.
Providing Free Trials in the App Store? by Sasmito Adibowo