Social relation

How do I become talkative and able to engage people to have conversation with me. When I see the person I know, I always smile and greet them and they do the same to me(I try to mean those people don't seem to dislike me). I don't find any topic to talk longer with them as they are just people I talked few times. But I notice that when I go with somebody and run into other we know, that person greets me warmly as I do and start go on talking with the one I am going with. That makes me feel little bit down. Then, I assume that person is closer to my friend that's why she talks more with my friend and even they took half an hour talking to each other while I stand by and when I try to take part of the conversation, quite often I'm like ignored or my speech is not noticeable or inaudible to them, but I come to know that they also kinda just know each other's face and when I ask about them they barely remember the name of that person they talked closely with. So, I concluded that they have ability to invoke comfortable conversation with anybody. So, I decided to grow talkative and be more comfortable when running into a person. Basically, when I see a person I know, I say "Hi, how are you? How's your studies or class going on? bla bla bla" and pass by, because usually people talk to me briefly. Can you guys suggest me some practical approaches? (if you are interested, please rephrase and correct what I wrote for my better English)