set up:建立,创立
A new government was set up after the war.
新政府于战后成立.
set down:记下
I have set down all the things that happened.
我已将发生的所有事记了下来.
set out:出发,开始.（后加不定式,即set out to do sth）
He set out to paint the whole house but finished only the front part.
他开始着手粉刷整幢房子,可是只完成了前面的部分.
set about:开始,着手.与set out意思相近（但后加 ing形式,即set about doing sth.）
He set about learning Chinese at age ten.
他在十岁时开始学中文.