Tom — it totally depends on the lady in your life. If she is really special to you then you will know what makes her happy and how to go about getting or doing the right thing!
It all takes a bit of thought and forward planning — you may not get it spot on every time but you should be seen to be doing your best. Taking advice from others as to how to best please the special person in your life is not really a good start as they won't know what really pleases your special person!
To some ladies "Hallmark Day" is a load of over commercialised crap while others just want you to be romantic and that does not always mean spending a lot of money. Others however may want you to open your wallet and just be generous towards her — they are all different and can all be just as special.