You will likely need girl psychology to ever get everything right, so give it up and learn as you go lol 
I've certainly learnt that a lot of the times, it's not that the bf doesn't care, it's simply that he doesn't know. I've found most guys don't seem to understand the concept of "it's not what you say, it's how you say it" or "you need to want to do it"

etc lol.
Ok, as to your question - little things would do for me really. For example - hold the girl's hand in public. To a guy when a girl complains, he thinks: "But you know I love you, so what's the problem?" - and to a girl she thinks: "But don't you want to show the world that you love me and I'm yours?"
^that's certainly how I think anyway - I'm sure there will be some girls that will differ, of course.
And anniversaries - I think to most girls, certainly to me, it's very important. The girl thinks: "It's a special day because I met you then/started this relationship with you then, since you are special to me." The bf thinks: "A day on which I must spend all my time hanging out with her and must not do anything else, and I must spend money to treat her out or a present but I'm poor since I'm a student... hassle. Besides, it's just a normal day like any other day." - oh and, never fail to do something special for her, or if you're in another place from her, never fail to be the first to ring her (or if it's Christmas or a birthday) Most girls would be deeply hurt and offended when the guy forgets.
A girl generally appreciates compliments, sweet comments of love and how great she is and how much you love her, small presents every now and again, paying for a meal or cinema now and again, walking her home even though you're tired and it's late, cooking for her, carrying her coat and bags for her etc. I'm the romantic mushy sort, so I greatly appreciate a small present or cooking for me etc - the typical stuff - and it's romantic just cus he thought of it, you know? Like, my bf gave me an Underworld poster today as a random present

It's not a romantic gift, but it's a romantic gesture and it's cute and I loved it
Anyway, like I said, what you really need is lessons in female psychology lol. I'm only just starting to grasp male psychology lol.