I'm an advanced driver - same qualifications as Crabs25.
My advice for motorway driving is this:-
1. Keep a steady distance between you and the vehicle in front. Make sure that you will have plenty of time to react should the worst happen ahead.
2. Stick to the speed limit for that road. It's the law of the land and is there for a purpose - to protect life and reduce the number of KSI's (Killed or Serous Injury RTC's). I know that some people would argue that cars now are more than capable of stopping from high speed quicker than the the Highway Code states and that the speed limit should be increased (or as I've seen from some in this thread - ignored). It is not the car but the driver than needs to be taken into account. While I agree that some may be able to drive at high speed you MUST take into consideration the skills and experience of the other road users and any other issues that you might come across- i.e. a tyre blowout, debris on an unlit section, a car crashed in your lane which you cannot see at night (believe me, that DOES happen and I've dealt with the results of one such) - all sorts of issues. Drive above the speed limit and get points. Drive above 100mph and face a ban and all the insurance costing implications that involves - or worse still - kill or injure someone due to excessive speed and face upto 14 years in prison for S1 RTA 1988 - causing death by dangerous driving.
3. Observe lane discipline - as has been said before, Lane 1 is the main lane and the others are for overtaking only.
4. Try to avoid harsh braking (see point 1). We all get stuck in long tail backs only to find nothing at the head. Well, most of this is caused by lack of distance and braking, this causes a concertina effect further back which after a few miles means stationary traffic and frustrated drivers - so easy to avoid by keeping distance and watching ahead! The motorway backs up at a rate on 1 mile per minute at busy times (more on the M6 or the M25!
5. Keep relaxed - despite what others say there is nothing wrong with being relaxed while driving. However, you MUST stay alert. If you find your alertness drifting then concentrate, if that becomes hard then stop at the next services and take a break - don't become like some posters and drive like a madman to keep alert, you're asking for a ticket or a crash that way.
6. Slow down in reduced visibility. Today I drove back from the Lake District and the view distance was reduced by spray to about 100m and so I reduced my speed - I got in a nice space between a line of trucks out of the spray and I set my cruise to match theirs - no braking was needed (unlike the fools passing at high speed) and I was out of the worst of the spray. I saw a large number of idiots pass me at speeds I would estimate to be 90 to 100mph (and yes, I am an expert at judging speed).
7. Give foreign registered HGV's a really wide berth. Pass in lane 3 if safe and you're not going to hold up drivers already in that lane. If lane 3 is not available then WAIT to pass until you have a clear run through - accelerate past (within the speed limit) in one fluid movement. DO NOT SIT ALONG SIDE IF AT ALL POSSIBLE, doing this is asking for trouble and the number of 'Blind Spot' RTC's is on the increase.
8. If possible give yourself an escape route. What I mean by this is be aware of your surroundings and try to drive staggered from the vehicles around you. That way if you need to you can change lanes to avoid a collision. This is not always possible or practical (in heavy stationary traffic or when passing in lane 3) but it's a good thing to be aware of - especially when passing 'heavies'.
9. Do not undertake unless the lane to your right is slowing and yours is not. The Highway Code allows for this as some have already noted - but it does not allow for lane changes to undertake a few cars that are driving slower in your lane. You MUST wait for them to clear you lane and then OVERTAKE. That type of undertake is extremely dangerous and one I NEVER do - and believe me there have been times when I've really needed to get somewhere fast on the motorway but have been held up for several miles - but I have not undertaken as I want to go home without broken bones or a death on my conscience.
Most of all, stay safe and drive responsibly. Fuel or speed should not be your first consideration - safety is always paramount when driving anywhere, but especially so when driving on the motorway.
Rich