Is there a way to talk to ladies to continue conversation!

well in my way when a men approach a women he should be polite and sincere,and that ladies should respect that,yesterday i had an incident when i helped an old lady to carry bags for her,after that when i was walking the street one beautiful lady asked me that was a good deed that i have done,i went too politely that the conversation ended quickly with her,i thought to ask dinner and a phone number,but she ended saying maybe later,what could that possibly mean,anyway nothing wrong with my looks though could ya give me tips on how i get a lady for a dinner and how i can ask for a phone number,just some few dating tips.