energy waste (physics)

That's a simple question which can be found on Google. Go do the research yourself.

Hi!

It very much depends what kind of 'energy' you are referring to, so I'll try to give some (hopefully) helpful examples!

If you're transferring heat, in a house for instance, you could do things like having loft insulation, double glazing, installing carpets, draught excluders etc, as these will all be good at preventing the heat from leaving the entire 'house system'.
You can also do things like make sure all lights are turned off when you don't need them on, as this is unnecessary energy expenditure, and the same can be said for things like running taps.

In an experimental sense, like if you're looking at something like specific heat capacity and you're using a water bath, you would want to insulate that by wrapping some cloths around it and placing it in a larger beaker, as this will reduce the amount of heat lost to the surroundings.

My final take on the matter is that energy efficiency is about useful energy out/total energy in, so energy is only 'wasted' if it isn't useful to the user, so energy wastage can be quite subjective!

Hope that was some help!