What I sometimes do, in preparation for rehearsals and service, is to record myself playing along to the original song. Learn how to record.
It may be time-consuming, but it is a really good way to improve. You get to hear your mistakes, stuff that you never knew you made. And you know you're 'there' where your playing really blends in with the music. It's also great to check if the instrument parts blend in, esp if you have two guitars - just layer the guitars and see how it sounds.
Here are some examples of the recordings I've made at home in preparation for rehearsals in church.. the guitar is usually quite overwhelming as I wanted to check how the two guitar parts blend in. I'll update the list as I record more:
If you have/are going to have such recordings, do post them up in the 'recordings/compositions' section of the guitarpraise forum - many of us would like to give constructive comments and help you out!