Some sources would urge you against including a photo but I personally believe that a photo can make your resume more personal, allowing employers to put a face to a name.
It is vital, though, that you dress appropriately and have your photo professionally taken, otherwise it will undermine rather than strengthen your application. It partly depends on the type of position you’re applying for, but the general recommendation is to dress in a businesslike manner and avoid extremes, such as extra short skirts, low cut shirts, clothes that don’t fit well, or very casual attire.
There should be no other people in the photo and the background should be plain. Avoid cropping your photo from a group shot or just using one of your holiday snaps.