Getting image size right in Lightroom on Export is all about aspect ratio. But, what about PPI (Pixels Per Inch)? PPI only matters if you intend to print the image, via an Bureau for instance. I cover the subject in detail in this NEW VIDEO, with particular emphasis on getting print dimensions right.
Link to Jeffrey Friedl's JPG quality article: http://regex.info/blog/lightroom-good...
JPG Plugin: http://regex.info/blog/lightroom-good...