forgetting the past and move on??

Well, tomorrow is the start of the term. When i was a kid at school, i was always enthusiastic about a new beginning, a fresh start but now, it has somewhat faded away.
Well, i will be meeting those people again, those whom i'll be overwhelmed to see again and those who i don't really want to come across, never!
But what is really whispering at the back of my mind is that there has always been some people on campus who would like to know about me, they tried to smile at me, but me, huh..as i am..i think that sometimes maybe out of shyness, i do not want to respond to them or perhaps it may be sheer arrogance. I am myself confused about my feelings for such types of people. Can someone help me here, please!
I know i am not arrogant but perhaps sometimes i can just take over me...
the question is that should i really respond to these people, i know i should not be bothered about perfect strangers, but the fact that they come across you everyday, you are bound to... i don't know...
is it that i should smile back...out of courtesy...what is this shyness thing about!! 
i feel really strange...well, can somebody just lighten me a little about this type of attitude of mine!! What should i really do? I know it might sound ridiculous! But it's what we are here for... thanks :)