Aspect ratio issues plague many photographers, new and seasoned.
There are photographers I work with that have been shooting for years that still demand an uncropped 8x10 or 11x14 from a 3:2 aspect ratio file all of the time and they still don't get that it can't be done without cropping or distorting the image.
This diagram shows the amount of an image that is lost from a 3:2 aspect ratio sensor when making "standard" sized enlargements.
I enlarge hundreds of photographs a week for clients and the majority are not to the correct aspect ratio. Some can be cropped without impacting the image others can't, in those cases I add black or white borders as needed to keep the original impact of the image.
Current 3:2 aspect ratio cameras (95% or more of all SLR's, see last paragraph) print to 4x6, 6x9 (if your lab offers it), 8x12, 12x18, 16x24 & 20x30 without cropping. Any other size including 5x7, 8x10 and 11x14 require cropping or another form of layout if you want to print full bleed (image all the way to the edge of the paper).
Personally I prefer the look of full bleed over bordered prints and usually suggest adding including an additional 20 - 25% around a subject while shooting for later cropping.
This information is less important when using a 4:3 aspect ratio camera or a point and shoot as the crop will be far less dramatic. The exception is when printing 4x6" photos, 4:3 ratio cameras would print a 4.5x6" so you are going to lose 1/2" from somewhere when making "standard" print from your Canon G11 or Olympus E-620.