Discourse markers
Zaffar from India writes:
  Please help me out. The expression mind you has been confusing me for some time in many ways. Please help me to understand this expression.
Roger Woodham replies:
Discourse markers or linking words like mind you indicate how one piece of discourse is connected to another piece of discourse. They show the connection between what has already been written or said and what is going to be written or said. Some are very informal and characteristic of spoken language. Others are quite formal and characteristic of written language. There are many of them. The following represent a tiny fraction of the total.
mind you / still
Mind you is an example of an informal linking device used in spoken English to point out that what you are going to say as an afterthought contradicts what has already been said. Still can be used in a similar way:
Miners in this country work for long hours in very difficult conditions and mostly in the dark. Mind you, they’re well paid for the work they do.
The divorce was very acrimonious and she didn't get half of what she was expecting. Still, she's been left with a comfortable house to bring the children up in.
by the way / incidentally
By the way and incidentally can also be used to introduce afterthoughts but they do not contradict what has already been said like mind you or still. But they do indicate a change in direction of the conversation. Both are used in informal and semi-formal spoken English. Incidentally is slightly more formal than by the way:
I'm meeting Tom at five o?clock to discuss the end-of-year balances and then I'm playing tennis with Greg. Oh, by the way, I shan't want anything to eat when I get home.
She should do well. She's highly intelligent, she has worked hard and done a lot of revision. Incidentally, her name is misspelt on the examination entry form.
however / nevertheless
Like mind you and still, however and nevertheless are used to introduce a contrast with what has been said before. However, they are much more characteristic of written English:
As expected, Britain has again come last in the European athletics championships. However, we did register one small success by coming third and winning the bronze in the hop, skip and jump.
He is unlikely ever to get into the first team and I know he is keen to return to his native country at the earliest opportunity. Nevertheless, he will be expected to fulfil his contract and remain with us until the end of the summer.
Note from these examples that in an informal medium, mind you and still could replace however and nevertheless.
you know / like / let's see
You know, like and let's see are all examples of a special kind of discourse marker used in conversation and they are known as fillers. They are employed to give the speaker a second to think about what he wants to say.
Like is very heavily used as a filler at the moment, especially by young adults and teenagers. For many young people it has become a speech habit. Here are some examples of use:
That strong wind that caused all the damage to the beach huts. That was back in ?like / let's see ?October?
I don't ever throw my rubbish away in the street. I ?like / you know ?care about the environment and stuff.
She didn't get the joke! I'm ?like ?laughing my head off, but she couldn't see what was funny about it.
He phoned me to say it was all over. I said ?like ?you can't do that to me.
You’re from Tunbridge Wells. That's ?like / let's see ?south of London?
He was rapping away like Eminem. And I'm ?like ?wow!