Some good websites out there, fang.com is probably the best, both landlords and agents use it, agents will obviously charge a fee, avoid the agencies targeting expats as they will overcharge you for everything (rent, bills, fee, ...) and overall avoid English speaking agents, bring in a Chinese friend with you who can read the lease contract.

In Beijing the further from Guomao and Tiananmen/Wangfujing the cheaper, anything beyond the 5th ring road will be very cheap but that means more commute. Avoid Sanlitun if you are not into drinking or if you have a family, many expats there but not the type I would recommend.

    Prepare yourself for the huge time-suck that is Chinese apartment hunting.  My advice, don't believe the pictures you see.  The places "look" livable until you show up to have a look and find three inches of cooking grease all over the kitchen, broken cabinetry, and moldy walls throughout. 

     If you use an agent, they charge you one month's rent but you can be very specific about your needs.  Even then, they'll still try sell you crap wrapped in a bow.   If not and you search for (个人）, every landlord will tell how clean and great their place is. 

     Finally, make sure your lease is iron-clad if renting from a landlord.  If there's a chance to get over on you, they'll take.  I speak from experience-I just got screwed by a landlord.

Are you looking to find a place for yourself or just a place you can share with a roommate?

If looking for a shared place, there are many websites to find them. If you can navigate the Chinese websites, I would recommend 58.com and ganji.com. 

If you are looking for a place for yourself, you can find places on those sites as well, but most listings will have been posted by agents, so you will pay them some commission fee when you sign the new lease. But if you go with an agent to find a place, and if you have the time, make them work for their commission. Don't settle for the first or second place they show you. If you don't like something about the place, make them find you another one. When I found my current place, I went through 3 or 4 agents, each showing me about 2 places, until I finally found a place that was the best deal for me.

They will try and dump a crappy place on you first. Make sure you say exactly you do and don't want. They will then so you stuff you don't want. If after a few places they are still showing you what you don't want tell them you are not happy with the service and find another company. Chances are there will be another in five minutes walk from where you are.

Thanks guys - this really helps. Went out with the first real estate dude today and saw some crappy stuff, so moving onto another man tomorrow.

In my opinion the most important aspect is the landlord. If he seems rich and aloof, take the place.  If its a middle aged woman, or anyone that kind of seems cheap, just run.  

The chinese that care about face alot, will act like money isnt an issue. Things will get replaced and youll get your deposit back without an argument. 

Cheap asses will blame you if their crappy washing machine breaks and will nickle and dime you when you leave.  

I cant stress it enough, try to find a cool landlord.  Lots of houses are comfortable.  

if you are renting, as against sharing, no matter how nice and friendly the landlord/landlady is, take pictures of the entire place before you move in.

This will ensure a digital record of the state of everything so they can't accuse you of doing something when you are looking for your deposit back.

paranoid? could be.

I would to this even at home when renting.

as per your place of employment, if possible keep a record of all your dealings with whoever should be taking care of maintenance.

hopefully you will find a good landlord, but remember you are still the foreigner and therefore the 'other'.

good luck !