When I add a narration, the voice is thin and soft. I am using my computer's built in mike.
Built-in microphones seldom have good tonal quality. You'll generally get better quality from an external mike. As for loudness, there are two mike volume controls -- one in the OS and one in Premiere Elements. Adjust the system setting first. In System Preferences select Sound. Then select the Input Tab. Select the mike you will be using and adjust the input volume slider. In Premiere Elements, there will be a volume control and levels meter in the record narration dialog.
When I bring in a still photo captured in 2x3 format, I have been cropping it in LR5 to 16x9 (the size of my HD video). I see there is another way: turn off "scale to fit frame size". Which is the best alternative?
If you are going to be panning or zooming, do not use Scale to Frame Size. Scale to Frame Size is fine if all you want to do is have the photo fit within the video frame. But, it will degrade the image if you subsequently scale it up as would happen in a pan or zoom.
Photos from a digital camera are large compared to a video frame. While Premiere Elements can scale these down, using full size photos increases memory requirements and can affect rendering times. Whether you will see any impact will depend, of course, on your system resources and compute power. Generally, it's considered a good practice to scale down photos to a reasonable working size before importing them into Premiere Elements.
In determining a size to use, consider the size of the video frame and the amount that you want to pan or zoom. The basic principle is that you don't want the scaling percentage to go over 100%. Steve's book recommends that photos be no larger than 1000 x 750 pixels for standard definition video or 2000 x 1500 for high definition video. This is just a guideline and you can certainly go larger if you need to zoom or pan further.
Lightroom can resize the photos as you export using the Image Size settings in the export module. If you want the photo to have the same proportions as the video frame, you can crop it to 16/9 in LightRoom as you have been doing.
When I click on RENDER after applying an effect (i.e. pan/zoom) I don't get a "pop up" box showing progress. Is rendering happening behind the scenes?
Is there a red line above the timeline? Generally, you will only see the render progress dialog if PRE actually needs to render. If the Line is green, no render is necessary.