(1)
try to do sth 尽力做某事
trying doing sth 尝试做某事
(2)
forget to do sth 忘记去做某事(还没做)
forget doing sth 忘记做过某事(已经做了)
(3)
remember to do sth 记得去做某事(还没做)
remember doing sth 记得做过某事(已经做了).