It has been said that you can edit video on your iPhone 3Gs, but this is not true. You can do just the most basic trims to the video, which is not to say that you can really cut things together and make sequences. The best advice here is then to “shoot to edit,” which means that you shoot short video clips on the iPhone that can then be assembled later individually in an outside computer non-linear editing software. If you do just want to record one long video, know that you can cut off from the beginning or end.