All digital photos have an EXIF orientation flag. To ensure the photo appears "right-side up" when taken in landscape mode, hold the iPad with the home button on the right when you take the photo. If you take a photo of yourself in landscape mode, make sure the home button is on the left. Otherwise make sure the home button is on the bottom for portrait mode.
It may not appear to make any difference on your iPad, but when you email photos the EXIF data is read by the other person's email program and will display it accordingly.
Hope that helps!