creepysusie

I recently had a conversation with a friend of mine and she told me that as she was walking home from the bus stop, some guy came up to her and said "You were so beautiful I just had to stop you and talk to you". As flattering as it was, she was understandably creeped out, especially since he asked her out for coffee immediately afterwards. Despite his good looks, she said that his approach was rather creepy.
She said no and the "I have a boyfriend" excuse and went along her way (She has also had a long list of random people come up to her before. My favourite come on "Your shoes match your coat, let's fuck". True story, I was there.). Afterwards she was kicking herself for not leaving a more open ended excuse.

QUESTION: How do you approach a stranger without coming off creepy or desperate? We had a long discussion on this matter and realized that I couldn't come to a conclusion. She had met her ex through friends and I met my boyfriend in university when we were put in the same project groups.

So how did you meet your partner and given the situation, how would you approach a total stranger for a date?