I wanna hit this time...what r the Do's and Dont's of the approach?

I have always been successful in attracting most of the women I come across.Mostly I or they themselves start the conversation ,everything goes wonderfully in the intial stages. But then after a week or so I lose her attention towards me. Well I have a good sense of humor and am very sure on that n also have a decent personality. So this time I met a one year senior girl in college she was sitting next to me in examination hall ,where we got introduced to each other.She was the one who started the conversation and was very humble and responsive towards me. Its been a week now since that day I didnt talked to her personally but whenever she pes by me in college she gives me her sweet smile with a "Hello good morning" written on it. Now I am gonna make my step and proced further to take her number and extend the relation. But some1 please advice me some Do's and Dont's coz I dont wanna be a victim of another Incomplete story and jus finish up becoming normal friendz ;-)...thnx for reading my Qs