Think twice before .../ think well
よく考える ー yoku kangaeru
1.試験取る前によく考える。- shiken toru maeni yoku kangaeru. - think twice before (you) take exam
2.パーチィ 入る前に よく考えてください -patyi irumaeni yokukangaetekudasai - think well before joint the party.
3.アメリにカ行く前によく考えてください - amerika ni iku maeni yoku kangaetekudasai - please think twice before you go to america.
4.彼に結婚する前によくかんがえる。 -kare ni kekkon suru maeni yoku kangaeru - thik twice before you married with him.
this phrase is more like idioms for think it well, let's try to make other sentence.

