Something that always bothers me is when my students are asked what should be done to save energy (or global warming, etc.) their answer is always the same - turn off the lights, turn off electronic equipment not being used, buy efficient equipment, blah, blah, ...
While these answers are good for themselves, I really wish they would consider the whole picture and think about what could be done to seriously help the environment.
Water How to conserve: "Don't run water when you brush your teeth". OK, but almost 80% of all water worldwide is used by agriculture. What we therefore need is a radical rethink of the way agriculture is done. Today's agriculture is mostly monoculture, highly irrigated, large-scale, corporate farms.
What we really need to look at is Water Security as the UN recently discussed.
Energy and Global Warming Turning off the lights is a good idea, but it does not address the large-scale inefficiencies of industry, utilities, etc. And to solve issues such as global warming we must phase out using fossil fuels as soon as possible. Other things include removing oil subsidies, improving power grids and using micropower instead of macropower.
Even though we try to push renewable energy the students still parrot the phrases such as "sun does not shine all the time" or "the wind does always blow", but ignore the developments in energy storage and distribution. On the other hand they seem not to understand that are some concerns about (first generation) biomass.
Solid Waste and Water Pollution "Don't throw trash in the water" (solves two things at once!). For water pollution this is a small part of the problem. Human waste (sewage) and effluents from factories are much more important. For solid waste it does not actually reduce the amount of waste generated and therefore does not solve the waste problem (it solves littering but that is another issue).
"Pass a law" - the cop out answer. I have seen it in everything from solid waste to air pollution to biodiversity. Of course my response is always what law should be passed, what specific aspects are to be regulated, enforcement, and numerous other issues.
My real goal is to make people understand the problem not simply give me memorized expressions that have no meaning.