I had a friend who thought he didn't smell, but his BO was horrible. I would sometimes go out of my way to avoid him. It's not like we didn't tell him either, he just didn't believe us. Who knows why.
Anyways for me:
-Shower in the morning / Shower at night after a workout / Shower before going out.
-Old Spice Deodorant twice a day, smells great too.
-Brush teeth after every meal, and again if my mouth doesn't feel completely fresh.
-Shave regularly, unless it's summer. I let it go a bit during the summer, but still shave every week or so.
-I only use cologne if I'm going out, otherwise I find my that my Old Spice deodorant tends to be pretty good at that fresh smell.