I TY to do nice things for other people (including strangers).

I have paid the difference in someones shopping before, left the $1 in the trolley for the next person who couldn't find a coin.
I do it to help someone else out plain and simple, i'd also hope that IF i was ever a couple of $$ short someone might say here don't worry.

If i help a friend i do it because they are my friend, not because they MIGHT get me a gift or it means they owe me, thats not how i work.