well a good example is...
i was at a store and they didnt have the pants i wanted on sale, so i asked the hot lady who worked there to write down the style number for me, and while she was writing i easily couldve said something funny like 'why dont you write your number down too, then when i go looking for thepants you can come wiht me' or something along those lines
or just the old 'whats your phone number?'
another one-- i was leaving a new years eve party early because i had to march in the rose parade, the girl said 'ill be looking for you in the parade' and i said 'how about you give me yuor number, and ill call you when im on tv and wave and say hi' and she gave it to me of course....
you just gotta practice, thats the most important part, start with 'whats your phone number?' and move on to complicated things based on the situation, like hwat i did