How do i give my number to a guy without looking "easy"?

I'm back dating after getting out of a bad relationship a few years ago. I was out at the movies with my friend girls and we had noticed a group of guys we walked past them and one immediately came up to me. He asked my name and age then if I was single, then he asked for my number to "get to know me better". I thought he was attractive and he seemed nice, so I gave him my number. When I walked back over to my friend she jokingly called me a slut and said "why did you give him your number you don't know him"..that was a dumb comment to me because how else would I get to know him if I didn't give him my number. We talked to my mom about it and she said that they had probably been sitting there getting numbers from every girl that went by, but I just don't think negative about all guys that approach me. My sister said I should of just taken his number and call him on my time, that wouldn't of "made you look so easy and would of started a chase, guys love a chase and mystery". I just don't see a reason to play games..I did not end up dating this guy we just weren't a match and ended up not talking again after a week. The same thing happened at the mall when I gave my number to a guy and my friend was saying I shouldn't give my number out to guys I just meet...am I wrong for doing that? I don't give my number to every guy that approaches me only the ones I'm interested in. How do I go about giving my number to a guy I meet out? Are there questions I need to ask? Do we need to sit and talk for awhile first? I was in a relationship for 5 years the last time I "picked up a guy" I was 16 years old. Please give me sme advice