For or During?

'During' denotes a general period of time....For example..I played the guitar during my lunch time which could be for 20 mins or 1 hour.

'For' denotes a specific period of time. For example I played the guitar for 30 mins.

Covering Letter

Correcting your covering letters I've found that most of you used the greeting and closing formula given in the book. It's good you use sentences that you know are correct because after all, in this type of letters, we tend to use set expressions. But I've found this sample letter with a few more example you can use, may you have to write a cover letter in real life.

http://www.ncirl.ie/dynamic/File/Cover%20Letter%20Handout%20Amended%20Links.pdf

Se pilla antes a un mentiroso que a un cojo

"The truth will out" o "Lies have short legs"

Tag Questions - Is he not?

Here is a full explanation on tag questions, or question tags as they call it in the book.
http://www.eflnet.com/tutorials/tagquestions.php

Aguardiente

People were asking the other day the translation for "aguardiente". I'm no alcohol expert, but it seems to me that countries that traditionally make this drink are Spanish speaking countries. In this thread some people say aguardiente, some people say "firewater" would be understood, and they also talk about moon-shine, but I'm not sure it's made with the same ingredents because I'd say they don't grow them in England or the US due to the weather. I know of an illegal homemade drink in Ireland, made out of potatoes, called Poitín in Gaelic and anglicised as Potcheen. People would drink a glass of this drink, they'd get drunk out of their faces, sleep, and the following morning they'd drink water and get drunk again. That's how strong it was.
http://www.wordreference.com/es/en/translation.asp?spen=aguardiente

Computer (repair) technician

I've found this wiki defining Computer repair technician, which seems to that it could be the person who repairs computers.

http://en.wikipedia.org/wiki/Computer_repair_technician

Using Adjectives when Writing

In both Intermediate 1 and 2, we're looking at adjectives in the current unit. Even though we're learning different grammar and vocabulary, it's important to bear in main their practical use and how many possibilities they give us. Englisg people, when writing, use adjectives a lot. Here is a video that may give you ideas for your writings.
http://www.youtube.com/watch?v=FxYhbR3FpL8