Just drop me a line when you decide on a date. 一旦你确定了日期给我写信就行。
I hadn't heard from John in ages so I thought I'd drop him a line.
Could you drop her a line and ask her where she got her tent? I'd love to get one myself.
Drop us a line and we'll put your query to our panel of experts.
If I haven't heard from Amber by next weekend I'll drop her a line.
See also: drop verb (FALL)