Students tend to travel longer term and on a budget, so I assume you would be as well, and that don’t want a 4-5 star hotel (although you can certainly meet travelers there, just not primarily other young students.) A budget place I have not stayed at nor seen is the Hop Inn, it seems to get good recocs here and quite good ones on tripadivsor.com. The only website I can find is at http://www.hostels.com/hostels/hong-kong/hop-inn/39944, take a look at this, it may give you links to other low-budget places. This is in a good location for Kowloon. I agree that the Lonely Planet guidebook and Thorn Tree Posts site would be a good place to look as well. On tripadvisor.com you can search by price which might be a good way to do your search.

There are the sort of infamous Chungking Mansions also in Kowloon, lots of small apartment-hotels there. There are some crime issues (in a city which has virtually no crime), so I would be careful if you stay there. But certainly full of backpacking students. I believe it is covered in the Lonely Planet guide, otherwise just walk around and inspect a few places before choosing one.

I would also say to look at the various YMCAs in town which operate hotels, there are several which may work, the website for all YMCA hotels in Asia is /www.ymca-hotels.com. Also try the YWCA’s which have hotels, see http://hotel.ywca.org.hk/eng/Mainpage/index.htm. None of these are really cheap, but have good facilities and most have a good location. There is a hotel run by the Boy Scouts in Kowloon, see http://www.bpih.com.hk/; its not really a hostel or low-budget hotel but might be worth considering

There are also hostels in town run by the Jockey Club, the location of these does not tend to be great, as all but the Mt Davis hostel are in somewhat to very isolated country park areas of the New Territories or outlying islands. And the Mt Davis hostel is a bit isolated. But look at http://www.hihostels.com/dba/hostels-Hong-Kong.

A final thought is one of the dorms/residences at the University of Hong Kong, see http://www.hku.hk/facilities/. I don’t know that they take short-term accommodation, but you might check. If you are enrolled in a university currently at home, you may be able to get accommodations through your school at HKU or another university in Hong Kong. HKU is on Hong Kong Island and so has a good location from that standpoint, but it is not in the main city area and you would primarily be meeting local Hong Kong students plus a smaller number of foreign students. Not sure if this is what you had in mind.

At your age, the best bar area is probably Lan Kwai Fong which is in Central on Hong Kong Island, although the bar areas of Wan Chai may also appeal. Knutsford Terrace on the Kowloon side may also work, I think that is more tourists and young locals, who may be on the shy side as opposed to people you would meet in LKF. Wan Chai has more than a little bit of the “bar girl” type places, again not sure if that appeals.