Remember that in the qualifying heats that the only thing you are racing is the clock. You are not racing the other cars on the track. Concentrate on getting around the track in the fastest possible time and do everything possible to avoid collisions - two or three crashes in a race will usually cost you a lap or more. So avoiding collisions, either with other cars or the track barriers, will improve the number of laps you complete and the higher you will qualify.
The only time you should race other cars is during the finals and then only when the cars are on the same lap. If you are lapping or being lapped then the guidelines above should be followed.
You are fully entitled to make your car as wide as possible to prevent the other driver getting past. However, do not swerve to barge the other car off the track as they get past. It is bad driving and will cost you time.
The best way not to be overtaken is to stick to the racing line. If the other car tries to cut in even tighter then you may try to stop the other car from overtaking (but don't push it off the track). If the other car gets the nose of their car ahead of yours then they have the place and you should give way.
The other driver will do everything they reasonably can to stop you from overtaking and it is your responsibility to make sure that you pass cleanly without contact with the other car.
The best way of doing this is to stay close behind the other car (but not too close that you touch). The other driver will start to focus on your car and will be more likely to make a mistake and allow you to get past. Wait for a suitable passing opportunity such as running wide on the exit of a corner or being delayed by a car being lapped.
If no such opportunities arise then you will need to come up with other tactics such as finding out places on the track where you are quicker than they are and perhaps trying alternative racing lines so that you can approach the corner quicker than they can. However, do not use this to barge your way past.
If you make contact with the other car so that they crash or slow down, then you have passed the car unfairly so you should wait and let the other driver retake the place.
If another car is faster than you, then move over to one side to let it past. The best way of doing this is to run wide at the first available slow corner and letting the faster car take the racing line. By doing this you will hardly lose any time at all. However, be aware that the other car may try and overtake you on other places on the track. If the other driver tries to do this then ease off the throttle and let him get past you. Trying to block the driver is not good practice as it will slow both you and the other car down and is likely to lead to a collision with could cost you a lot of time.
If the other car is only marginally quicker or no quicker than you then it will be worthwhile letting them pass and drop slightly back behind them. If you don't, your focus will be on their car rather than concentrating on your racing lines. The result will be a slower time for both drivers.
Remember - try to anticipate when the other driver will try and pass you - slowing down by a fraction will save you a lot of time than carrying on at full speed and crashing.
If you are coming up to overtake a faster car then don't expect it to move over straight away as it may not be a suitable place to do so. Instead stay behind the car until you find a safe place to pass or the car moves to one side to let you through. Losing a fraction of a second by slowing down for a few corners is much better than a crash which could cost you many seconds. Even if the car is a lot slower than you, knocking the car off so you can get past quickly is totally unacceptable.
The safest place to pass other cars are by taking the inside line on slow corners, on the straight (don't get too close to the other car otherwise just a touch will send both off the track) or wait for the other car to make a mistake.
If you are coming up to a slower car then do not immediately shout out lapping. You should give the other driver the chance to move aside at a suitable place. Only if you are being held up for half a lap or more should you give the driver a reminder by calling the driver's name or car colour(s) and state that you are lapping.
If the car you are overtaking is the same speed as yours then unless you are confident that you can make the pass cleanly, stay behind the car and concentrate on your own lines. Only if the other car is being lapped should you call out for the car to move aside. If you are both on the same lap or even the other car is at least a lap in front, then just concentrate on your own lines or even consider dropping back slightly to avoid any potential collisions.
Remember - it is your responsibility to overtake other cars without hitting them. Even if this means staying behind them for a few corners.
(thankyou to Chippenham Model Car Club and Ray Chiu)