Here is a good tutorial explaining the "How-to" in Photoshop:
You will see that there are several options for the perspective: Auto, Cylindrical, Reposition, etc. And there is a link that goes to an explanation of each one. Some might be more appropriate for the look you are trying to achieve and for the particular perspective in which you made your original images.
In Photoshop Elements v.11 you have the same options shown plus one called Interactive but they are found under the edit menu "Enhance": pull down to find "Photomerge", "Photomerge Panorama". I think older versions of Elements follow the menu shown in the tutorial.
Try the different options to see what works best. I have had the best luck with Reposition and Auto.
I found it interesting to take note of the layer masks that are created in the process--curvy squiggles on each of the individual images where the software finds the best places to merge them. Try doing that manually! [view them in the right hand column showing layers].
In addition, Photoshop and Elements offer to fill in those gaps left at the top and bottom based on surrounding content. I only do this if they are very small. I don't trust it to fill in large gaps.
If you have tips on shooting or using software, please add them in a comment below.
Hope we don't freeze Sunday for the workshop!