Wearing a cologne is always a good thing, It'll help her recognize u or remember something about u, key is to always make her think of u.
Next part is tricky, not to wear too much.. Wear enough so she can barely smell it.. If she likes what she smells but can't really smell it.. She'll try to smell u without u noticing.. Again key here is to have her thinking about u even when on a date with u
Yes always wear cologne when going out in public, if you smell good it will help the women recognize and remember you, plus it shows you respect hygiene. But you don't want to wear to much or to little like cantsaylol said. My personally cologne is the not well known Caswell Massey's Number 6 which is thee exact same cologne our founding father and first president George Washington wore. And let me tell you boy does it smell intoxicating both women and men love it, it lasts a long time to and separates me from everyone else since it has a unique smell.