Don't use pick-up lines, if your girlfriend is heavier then you are
If your girlfriend is lighter than you are, only then should you use pick-up lines
Say your allergic to her perfume, or other scented fragrance
Ask if it's bad that she smells remarkably better then you do.
Always be honest...
If you say you can juggle 5 chain saws AND her at the same time, you better be able to do it.
Always return compliments with 'oh i bet you say that to every guy you sleep with'