on one's turf — on one's own territory [see turf]

When you are surfing internet and watching webpages, do you know that the webpages may be watching you at the same time? Someone in my research group sets up a webpage and records the visitors' activities on the page. From the logs, he is able to reel back to any time in the past and replay what happened then, including who visited the webpage, from which domain, the duration of their stay and the links they clicked. This is, perhaps, arguable whether it invades visitors' privacy. Another guy justifies this for him: "He owns the log files. So he's working on his turf." Indeed.

hit if off — to get along well together [urban]

On 'Friends', Ross was glad that his wife, Carol, got to know a new friend, Susan. However, he wouldn't be if he had known earlier that Susan was a lesbian. He told Phoebe: "Susan and Carol met in a gym. They really hit it off."

pay off — to bribe [dict]

Last night, I attended a group discussion on the book 'Da Vinci Code', organized by the local Christians in Cambridge. I have no religion. Yet, I am interested to find out what Christians think about this "anti-Christian" book. To my surprise, the invited speaker was quite open-minded. He actually encouraged the audience to read the book and watch the forthcoming film, as he believed the judgement must be left to the audience themselves. When I told this to a Christian friend, he couldn't believe this. "Was he paid off by Sony Pictures?" he asked me.

sell someone down the river — to betray someone who trusts you [freedict]

On 'Prison Break', the vice-president was the mastermind behind the scene to frame Lincoln and put him on death penalty. She was backed by a powerful company, which financed her running for the presidency. However, after being messed up in the Lincoln's matter, she realized that the company no longer trusted her. She complained to her bodyguard: "The company is selling me down the river."

show someone the ropes — to explain to someone how to do a job or activity [thefreedict]

On 'The War at Home', Larry's little brother, Mike, is only 13 years old but very crafty. He concealed his age and asked a girl out for a date. Larry eagerly reminded Mike that the girl was 16, a lot older than Mike. With a cunning smile, Mike replied: "Then I don't need to show her the ropes."

break/bust someone's chops/ass — kid or embarrass someone [answers]

On 'The War at Home', Larry proudly told his father, Dave, that he got to know a pretty girl and manged to get her phone number. But when he tried to dial it, it turned out to be a wrong number. He was ready to dial again and asked Dave: "Does this look like 7 or 9?" Dave didn't believe his odd-looking son could hook up with any decent girl. "It's one," he said, "One in a million chance she gave you a real number." But noticing his son deeply upset by his teasing, he changed the tone: "ha ha, I am breaking your chops." Here is the origin of this idiom.

in the lurch — in a difficult or embarrassing position [dict]

The recent news on Shell's suspending Chip & Pin cards sparked a renewed debate over the security of the new payment system in the UK. Apparently the promised "infallible security" didn't deliver; banks had chosen to ignore the early warnings by experts in the field. From the ukcrypto forum, someone described his recent experience in a restaurant. Upon payment, the cashier refused his chip-and-pin card and nearly called the police. He reported this matter to his bank, but got little help as the bank was busy dealing with a number of similar cases. "They leave their customers in the lurch," he was disgruntled.

work one's tail off — Work especially hard [see wiki]

Someone told me that he worked very hard in a company. "I worked my tail off," he said. This idiom has the same meaning as "work one's fingers to the bone", but is more suitable for a light conversation.

dirty laundry — personal affairs that could be embarrassing if made public [dict]

On 'Desperate Housewives', Andrew, still a teenage, wants to get access to his trust fund prematurely. He proclaims that his mother, Bree, is an alcoholic and applies to the court to be emancipated. Andrew's grandparents try to meditate. They reprove Bree for having to handle the matter in court. But Bree rebuts: "Do you think I enjoy airing my dirty laundry in public?"

blue-sky — Unrealistic and impractical [dict]

Has your computer ever be hit by a computer virus? It's a pain to clean up the mess it causes. But imagine this: your computer suddenly stops working — no response from the mouse and the keyboard, the screen frozen, all files on the disk locked etc. Then you see the message on your screen: transfer 20 quids to the bank account xxxxx and everything will be back to normal in 2 seconds. Now we have a new member in the malware family: ransomware. This "evil" idea was first thought by someone in my research group and he wrote it up into a paper, but didn't publish it. "I had thought it was a blue-sky paper," he told us. But the threat is real now (see news).

gut feel/feeling — very rough estimate [wiktionary]

I was discussing with someone on the collaboration of a project. We were not sure whether our new method would work. He asked me, "What is your gut feel?" Noticing my puzzlement, he explained: "The equivalent word is: intuition." (It seems "gut feeling(s)" is more common that "gut feel" based on the results from google search.)

talk up — To speak in favor of; promote [dict]

In On Friends (note: this is a systematic error I've made so far. Thank Shawn for the correction), Ross was dating his young student Elizabeth. Before meeting his girlfriend's father in the coffee bar, Ross asked everyone to say good things about him in front of the future father-in-law (acted by Bruce Wills Willis, cool …). Later Rachel rushed into the coffee bar. Without knowing the girl's father was already sitting there, she said, "Sorry, Ross. I am late but I am ready to talk you up. So when does Liz's father get here?"

work (one’s) fingers to the bone — to work very hard for a very long time [freedict]

In Desperate Housewives, Gabrielle desperately wants to adopt a baby. But when she gets one, she hates the chore to take care of the baby. She asks her husband, Carlos, to hire a baby-sitter. But Carlos doesn’t agree. He insists that the new-born baby must be in touch with the mother. “When my mother raised me,” he says, “she worked fingers to the bone.”

crunch time — A period when pressure to succeed is great, often toward the end of an undertaking [dict]

Someone in my research group is writing up a paper for a conference. The submission deadline is only a few days ahead. He yawned and said to me, "It's crunch time now. I feel so tired…"