Resizing for Print

[nala]

I feel like I'm missing something really basic here, and I'm hoping someone can help. I'm trying to put together a few test images to send into an online printing company. They specified that they'd like the images to be sized 8x10 at 300ppi. I use Adobe Elements. The only way I could think of doing this is to go in and use the crop tool with those settings applied. The problem is that when I crop it, so much of the sides of the picture are left out that the photo doesn't look right anymore. Is there a better way to be resizing them (either in Elements or in the camera settings itself before taking the picture) or do most photographers just leave extra room around their photos when they're taking them to be able to crop them to 8x10 or 5x7 etc?

Thanks!!