Dear XX（教授的名字）
Sorry to disturb you!I am organizing an English lexture,and i want to invite you give the lecture about how to learn English well.The lecture will begin in the next Sunday.And it will be hold at the Multimedia lecture hall.If you are free then ,please tell me.I will apprecate you very much!Thanks for your time.
Yours student
XX(你的名字)
January3（日期写一下）
便条最主要的就是简单明了、希望能帮到你.时间地点你可以根据需要改一下子.用的是全齐头的方法……