MacBook can never find Printers

My MacBook Air can almost never find my printer on the network. It simply just doesn't show up as an option to add it. When I type in the printer's host name or IP address, it still can't find it. I'm in a dorm, so there are tens of printers, and most of the time, only about three of them show up as on the network. Then, every couple of days, I'll go to add the printer, and every printer in the building shows up as on network. I'll add it, and be able to print then, but then a few hours later, my computer shows the printer as offline, though its online, and can't find it? It's been a couple of months and I'm pretty sick of it. I need to print. How do I connect my printer?