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Neither old nor modern cars are supposed to idle at start up. The increased revs followed by the drop is the automatic choke (increased fuel to air ratio). The quicker you put the car under load, ie driving, the quicker it warms ups up and the quicker the auto choke disengages. Also, the exhaust emissions are at their dirtiest at cold start up so another reason to drive off immediately. This applies for petrol or diesel. Proof of this is if you let the car idle for 10 minutes from stone cold, it'll achieve only a very low engine temp. But using the method I have described, the car will take a fraction of the time to hit the same operating temperature and quickly go on to achieving normal operating temp.
In terms of driving hard, best practise is to let the oil/ water (subject to your model depends on what gauge you get) temperature hit normal, and by then the gearbox and diff oil will be up to working temp too. This will keep the innards safest. If you have an auto, avoid kick down and the 'box and ECU will prevent overrevving anyway, so just drive as normal. For manual 'boxes, I don't think there is any intervention, so refer to the manufacturers guidance for Rev limits.
At the other end of the drive, especially an enthusiastic one, idling the engine is actually good practice (this rule only applies only really applies for turbo/ supercharged engines). So my rule is, that for every mile driven, I let the car idle before I switch it off (ie, 100 miles driven, 100 seconds cool down) This protects the turbos from overheating ("heat soak").
Both methods will help ensure excellent longevity from mechanical components and help prevent expensive trips to the stealers later in the car's life.
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