how a friend supposed to be??

i don't really understand what do others think about how a friendship supposed to be...
to be honest, sometimes i feel really really (or i can say extremely) disappointed with those who i assume as my best friends... it seems like i'm always be the one who has the initiate to contact them first, put them on priority... and found they never searched for me if i'm not searching for them... on the other hand, i feel like i'm being left behind (some of them got new friends around them & almost got no time for me - maybe they think that i'm boring, coz i can't really catch what they used to talk about - hell yea, i just live in this city for 6 months with no friends around me, so how to know what they've been up to)...
i tried to look back at myself... about the way i treat my friends... i do have new friends... but, do i leave all the old friends behind??? do i stop contacting my old friends??? i'm busy with my work... n just have my weekend to hang out... then, sometimes i ask a friend to go out with me just for lunch and talk... means, i'm not forgetting my friends...   if i complain that they're too busy to talk to me, am i selfish?? coz i'm busy as well, but i still set some times to talk to my friends, though i have to stay late at night... 
IDK how important is myself for you... 
IDK whether i'm a good friend or not...
and please tell me how a friend supposed to be??? 


-Jezz