Not "We play tennis tomorrow." — say "We're playing tennis tomorrow.". 说你的计划，用 am / is / are + -ing。
试一试: Woman: Do you want to go to the gym this Friday? Man: Sorry, I can't. ___ my grandmother in the hospital. 选出那个男人会说的话。 (I visited / I'm visiting / I was visiting) 答案: I'm visiting — 这个星期五去看奶奶是他的计划，所以说 I'm visiting。
问别人的计划
问别人的计划，把 am / is / are 放在人的前面：What are you doing on Saturday?
What are you doing on Saturday?
What are you doing after work?
Are you working tomorrow?
试一试: Man: What time ___ home tonight? Woman: Around nine. I have a late class. 选出那个男人会说的话。 (did you come / are you coming / do you come) 答案: are you coming — 今晚还没到，所以他问她几点回家：is coming。
时间表
说时间表，比如火车或课程的时间，用一般现在时：The train leaves at 9:15.
The train leaves at 9:15.
The store opens at ten tomorrow.
My class finishes at four.
试一试: Man: Excuse me. Where does the airport shuttle leave from? Woman: The main entrance. It ___ at 9:30. 选出那位女士会说的话。 (went / goes / going) 答案: goes — 机场班车的时间表上写着时间，所以用 goes：9:30 发车。
你的计划，还是时间表？
自己的计划：am / is / are + -ing。时间表：一般现在时。
I'm seeing a movie tonight. It starts at 8:30.
试一试: Ethan: Mei! Are you taking a train too? Mei: No. ___ someone. The ten o'clock train is on time. 选出 Mei 会说的话。 (I meet / I met / I'm meeting) 答案: I'm meeting — 去接人是她自己的计划，所以她说 I'm meeting。