Toilets, Sinks, Showers, Tubs and Disposals - consistent temperature

In my house there is inconsistency in the temperature of the water. Sometimes my shower is too warm, sometimes too cool. things are really impacted by other users like flushing toilets and running the dishwasher. I always accepted this as a function of home plumbing and resigned myself to accept that nothing could be done. That is until I stayed at a friends place for a while and noticed that there was absolutely no impact there to other household people. For instance, I could be in the shower and someone could flush the toilet just 2 feet away and there would be no perceptible change in water temperature (or pressure).

What I am wondering is, what are the variables at play here and what can I control. For instance, does changing the temperature on my water heater do anything? What about installing those no-scald faucets?

Thanks

What type of shower valve is it that your using, single and more then a single handle valve?

To follow up on the point made by Plumber2000: Modern shower valves have a pressure balanceing spool or other type of "anti-scald" feature. To replace your valve does require access inside the wall, either from the shower side or from the other side of that wall.