George is right. Both are used. In the first sentence the "me" is implied you assume that the person asking is the one who wants the salt. However, people often say me anyway.

The above answers regarding the technical meaning of momentum are all correct. I would add that momentum is also used outside of the context of science and math where people use it more conversationally. One might say for instance that a project is gaining momentum. This would mean that the project might have started off slow, with only a few people involved, but now it is moving along more quickly and more people have signed on to help. This is also true of political campaigns, kickstarter/crowdfunding/crowdsourcing campaigns anywhere where a critical mass of people is necessary. Momentum when used in this way is often synonymous with gaining traction.

code word is the correct word that you are looking for. I can't really think of any slang term for code word at the moment. A more natural way to say the sentence would be: Come on! You guys have been using code words all morning.

Neither of these phrases are used often in English conversation. However drop in on, means to visit unexpectedly. Call on is also a social visit the phrase was popular in the past but doesn't get much use now. It is something one's grandparents might say.

They are pretty much used interchangeably no real difference in the meanings.

I'm honestly not too familiar with the Economist. Time magazine however has a wider range of topics, and strives to be very up-to-date by covering recent events. Therefore I'd suggest Time magazine. If you are looking to improve your English reading comprehension and/or have the vocabulary to use in order to hold conversations on current topics you might also try Time online or the Huffington Post. By the way you want to use "advised" instead of advice in your original question.

The correct answer to your boss' question is "would be nice." Would be refers to the future. So it would be nice if my husband takes me to dinner for our anniversary next year. Would have been refers to the past. It would have been nice for use to go to dinner for our anniversary this year, but the baby was sick. I hope that explains the difference.

Recognize the signs can be used to mean symptoms (as in this case) clues, indicators that leads someone to a particular conclusion. In this instance the signs that the protagonist is referring to are the rubbery body and lack of tension which is leading him/her to a conclusion about what is wrong with the President.