I’ve been using a number of apps to take pictures with my iPhone. One called “Camera!” has worked well for regular shots.
I was also playing around with some that take panoramic shots. The DMD Dermandar seems to be the best and most user-friendly one I’ve found.
The quotation marks (shown in one of the images below) guide you through aligning the different shots correctly. Very easy to use. Make sure people aren’t moving in between shots.