What most naturally follows?

How to be sweet to your girlfriend
Tell her that you love her.
This is a fairly simple step, but it goes a long way. People that are in long-term relationships tend to forget, after the first month of dating, that they should say the simple words " i love you.
" simple works best, rather than long drawn out speeches about your overwhelming love for her. Casually mention it to her when she is particularly stressed.