Think (something) over
(決断する前に)...をじっくり考える、熟慮する、検討する (例): Think it over and let me know what you decide. じっくりと考えて決めたことを教えて。 Think things over- 状況についてじっくり考える
Think back
思い出す To remember and think about someone or something. Can you think back to your junior high days and tell me your best memory?
Try me
Ask me; give me a chance, test me (分かるから)聞いてみて、できるからやらせてみて(例): A: Can you cook? B: Try me. A:料理出来ますか？ B:できるよ! やらせてみ！
Turn in
提出する、手渡す to a teacher, the police, government etc. You need to turn in your notebooks. ノートを提出しなければなりません。
Up in the air
未決定である、はっきりしていない Our vacation plans are still up in the air. 休暇の計画はまだ固まっていません。
Were you not?
...じゃない？、でしょう？Weren't you? (Were you not? is the formal style of weren't you?)確認するための表現. Were you not in 1-A as a first year student?/You were in 1-A as a first-year student, were you not?
What for?
1. Why? 2. For what purpose? 何で？、どうして？、何のために？ What do you want to know that for?
What's up?
1. A greeting: How are you? How's it going? 元気かい？調子はどう？ 2. What's happening? What's going on? どうしたの？何かあったの？
Would you?
Would you/will you? 命令文の後に使って依頼表現として用いる場合は、余り丁寧な表現とは言えないため、親しい間柄に限った方賢明である ex. Open the window, would you? （窓を開けてくれ）
You better
〜した方がいい Shortened form of "You had better..." eg. You better go home now. （もう家に帰った方がいいぞ）