It's just a case of being as unobvious as possible. Your behaviour can be a key giveaway if you're smoking a J in public. Act relaxed and don't keep looking around suspiciously to check the coast is clear - that just makes it MORE obvious. If you know the patrols for your campus then just work it around that.
You can also vent your exhales into a sealed/airtight seal box. I know a few people (I'm from the UK) who exhale into an airtight box through a cheaply crafted one-way tube. Then, once they've finished, they just leave the box outside with the lid off for a few hours. It's a good way to keep your dorm/room smoke-free and also limit the smell from working its way into fabrics/carpets.
It all depends on your personal situation though.
You can also vent your exhales into a sealed/airtight seal box. I know a few people (I'm from the UK) who exhale into an airtight box through a cheaply crafted one-way tube. Then, once they've finished, they just leave the box outside with the lid off for a few hours. It's a good way to keep your dorm/room smoke-free and also limit the smell from working its way into fabrics/carpets.
It all depends on your personal situation though.