I said the "fast lane", but really it varies by conditions.
When driving an M5 - the fast lane is whichever lane I happen to occupy! 
On a highway, if there is a
good-sized median and moderate to heavy traffic, I like the most inside (number 1) lane because I generally have to be concerned only with traffic to my right. There are far fewer left exits/onramps than there are right exits/onramps, so by staying in the left-most lane there are fewer cars slowing to exit, cutting multiple lanes to avoid missing an exit, using the lane to accelerate to freeway speed, etc. I feel safest because I only have to anticipate idiotic maneuvers from drivers in front and to the right. If there is light traffic, I will usually choose the number 2 lane, except to pass, and leave the number 1 lane open to those going faster than me.
I will
almost always move to the number 2 lane to allow cars to pass, then resume the number 1 lane behind. That is, unless:
- the driver behind me tailgates while I am trying to find an opening to safely move right -- in that case, I'll stay left, accelerate and leave the jerk behind, or
- there is traffic just ahead of me that is going slower than my desired speed -- in that case, my moving right merely advances the guy behind me another 20 feet and puts me further behind, so why should I accommodate his impatience.
I agree that US drivers ignore the etiquette of moving right to allow faster traffic to pass. Many times, they seem to believe they are "enforcing" the speed limit. Actually, it may well be illegal to block the left lane to prevent someone from passing.
If there is a no adquate median, and a low barrier, or no barrier at all, dividing oncoming traffic, then the number 1 lane is less desirable, particularly if there is no inside shoulder. You run a bigger risk of a encountering debris in the number 1 lane, or a car parked in the lane due to a breakdown. There's also a higher risk of a car or wheel jumping the barrier or crossing the middle line. In that case, I tend to opt for the number 2 lane, and use the number 1 lane only for passing.
Similarly, if there is a steep shoulder, no right shoulder, or a drop off to the right, I may choose to stay one lane away from that.
In low visibility conditions, I tend to stay in the number two lane, because I have the benefit of the reflective markers on two sides to help keep me in the lane, and also a "cushion" lane between me and the median or oncoming traffic.
I also consider the road surface. I'll opt for the smoothest lane in dry conditions, but for the lane with the best traction if the road is wet. I find that the outside lanes (number 3 and 4) tend to be more heavily used by trucks, which cause additional wear on the pavement that can make the ride rougher than in the inside lanes, and can even produce ruts that cause the car to veer.
If there are 18 wheelers or SUVs in the lane, I'll try to move to where I have good forward visibility.
Basically, I make the lane choice I think best balances safety, speed and comfort for the particular road conditions.
Without any hesitation, my left hand middle and index fingers rest on high beam flasher. Be ready to give a friendly 'flash' to let the person front of me know that ///M5 is behind 
of what I call left-lane pirates. They grab the left lane and match speed with the car in the middle lane. Completely and utterly oblivious to anyone behind them. I'll never block anyone. In fact, I am happy for them to run the point for the local roving tax collectors.
I use the left lane for passing only and fall back in the middle or right lane depending on traffic. This also makes you less conspicious (see reference to tax collectors above).
Life in the Fast Lane
/ Caramel
Black/ Black & Grey E60 /// M5 Nicknamed Mighty M5 
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Linear Mode
