什么时候用look forward to,什么时候用be looking forward to

什么时候用look forward to,什么时候用be looking forward to 什么时候用look forward to,什么时候用be look forward to look forward to后面什么时候跟to do,什么时候用doing? look forward to 和be looking forward to有很多说法,这两个短语到底怎么用呢?好别扭! I’m looking forward to.和I look forward to.用的时候有什么区别? The day I looked forward to ------(come).为什么用came,那什么时候用look look forward to doing和looking forward to do look forward to 的后面什么时候动词不用加ing? 在商务信函中.结尾用Looking forward to >.这样可以吗?还是用Look forward to >. look forward to后是否能直接用be动词 I will be looking forward to it! I'll be looking forward to this