What do you say when you run into somebody, beside hello?

Make a positive comment such as, "I like your shoes/shirt...."). Or comment on haircut, colour of clothes, or whatever.

To be liked, generally, we need to be more interestED than interestING. Listening is good for making friends: ask people questions about themselves and their opinions and listen to them without interruption, except for little comments that demonstrate that you're REALLY listening. It shows you are taking them seriously, as in respect and acceptance. Don't sit there thinking about what you will say, because that shows more interest in yourself than them. Little pauses demonstrate that you are thinking about what they have said anyway. You can ask them how they felt about what they have just told you, or other specific questions to show you have been listening and taking them seriously. Be open minded and try not to disagree with people. For example, if they like a band you hate, ask what it is they like about them, best track, etc. (avoid the word, “why” as it can sound challenging). You can always say you don't listen to them much but you will now or something. Asking for advice is also good. Genuinely, of course, & don't overdo it. Ditto information – we feel pleased to tell someone something interesting they did not know, such as what’s on in town, latest sports score, etc., so by showing interest in their opinion, knowledge, etc. you’ll get some good feelings from them. Smiling is a good sign of acceptance. A lot of eye contact can also be good. Remember, if you want to have a friend, you have to BE a friend, and the best way to impress someone is to be impressed by them! One thing you can do is always to ensure you have a straight back: sit, stand and walk tall (hips forward) and take reasonably long, confident strides when you walk: this has the “reverse psychology” effect of helping us to feel more confident. Once we have self respect and a sense of self worth, we tend to find that other people respect us more too. Good Luck!

If you are both students, ask him about his classes and be prepared to tell him about yours.
Or think of some other common ground that you think he will be comfortable talking about...something you both experience or know about.
Keep it short, and if you would like, suggest coffee or cake at some specific day or time in the near future. A bit of time together when you are not each starting your commute will add to your list of shared experiences, and also give you a chance to learn a bit more about him, for purposes of future conversations. Build his knowledge of you, and yours of him. Then conversations can be started easier.