Speaking Chinese helps. You can get by with just English and rudimentary Chinese, but you're unlikely to make friends in tech.

If you can do an exchange semester at one of the Universities here (Tsinghua, PKU, BIT), do it. Doing a Chinese course at BCLU will also get you a student visa. Stay out of Wudaokou for the most part, much as I love the place, you'll just be insulated in the expat circle. Same goes for Sanlitun. Don't party with the BCLU kids too much.

Head over to Zhonguancun, there's this street called Innoway, you can hang out at Garage Cafe or something and get to know some Chinese tech people, practice some Chinese.

The really talkactive people you meet are nice people, but they're usually a bit full of shit. Take the things they say with a grain of salt. Good practice talking about technology in Chinese though.

Get Wechat. You need Wechat. There's a group called Beijing.py on there, they do tech meetups, which might be your beer (they also happen at Great Leap Brewery at lot, so there'll be actual beer). Get a Chinese bank account too, and a Chinese phone number.

You can always teach English. If you teach at a school, it's about 200RMB/hour part-time. You can do this on a dodgy visa.

You can rent a room at about 1500RMB/month in the Haidian area, where all the Universities and tech companies are. You can live off 2000-3000 RMB a month if you're willing to eat the cheap Chinese food. Bring Immodium.

There is a new regulation that allows people on student visas or with a University degree to work or found a tech company in the Haidian area. It came into effect this March. Costs about 6000RMB in registration costs.

Be aware of the air pollution, you might want to get a home filter for it, and wear a filter mask outside. They cost about 20RMB each and last 2-3 days. Get a smog alert app, but after a while you can tell PPM levels from the sky. Blue is 100odd, grayish brown is 200-300, if it looks like Silent Hill you're up in the nice 500s.

Winter is hellish, Summer is hellish. You get strong, cold winds during December, and Beijing turns into a humid baking pan in the Summer months. Heating is centrally controlled, and usually turns on 15 days after it gets really cold. So make sure where you live has an AC.

Traffic is hell, subway is cuddly, but it will get you where you need to be. Chinese have an interesting idea of what crossing the street looks like. When in doubt, walk over with a Chinese person standing between you and direction cars are approaching in.

If haggling is your thing, they're charging you 10x markup. If you're prepared to haggle for 4 hours, you might get the actual price. If not, order off taobao or jingdong instead. For taobao, if its tmall its legit, if its regular taobao look at the ratings and number of transactions.

Get a VPN before you arrive. AFAIK Viper is the preferred choice, and Astrill the most commonly used one. Their websites are blocked in China.

Don't do drugs. If they catch you, you're looking at being barred from the country for 10 years. They're not even good drugs either.

Be wary of cheap foreign liquor. Assume it was made in a bathtub. If you want to get really really drunk, buy cheap Baijiu at 7/11(12RMB for a .33 bottle) and chase it with Milk-tea (5RMB/bottle) to cut the burn. You won't remember the evening. Don't carry drugs on you when you do that. cf previous point.

Don't drink the tap water. If you must drink the tap water, boil it first. Otherwise, have immodium at the ready.

Laobeijing (Old Beijingers) have their own complex social customs. If you pour tea, you're supposed to hold the jug at the bottom if you're pouring for someone older, at the spout for someone your age, and at the top if you're pouring for someone younger. If you're being poured tea, you are supposed to tap both index fingers on the table. And that's just one thing. If you master the art, they'll appreciate it, but still look down on you for being a foreigner. They look down on Chinese migrants too though, so don't feel too bad about that.

Cabs are cheap and plenty, but Didi is cheaper. Don't get black cabs, they'll rip you off. When hailing a cab, stand at the side of the road, look at the direction of traffic, hold out your arm, and make a motion as if you're tapping a small child on the head. Airport cab ride is about 150RMB to Haidian. Airport express is about 20RMB, then you need to switch to the regular subway, which is another 3-6RMB.

Carry toilet paper on you if you're moving around. Toilets have about a 30% chance of providing toilet paper. Most toilets are squat toilets, though foreigner facing businesses may have sit down toilets. Stand on the sides and squat down backwards.

Don't withdraw large sums from ATMs, go to the bank counter for that. ATMs don't always check carefully for fake notes, and may recirculate them. I know of people who withdrew 20 100RMB notes and had 3 fakes in them.

Most places will accept WeChat and Alipay. This goes for small ruddy places too, they'll usually get you to send it to their smartphone. Do carry cash though in case they don't.

Well, this is getting pretty long.