Greetings & Social Basics

Hello: 你好 (Nǐ hǎo)

Thank you: 謝謝 (Xiè xiè)

You're welcome: 不客氣 (Bú kè qì)

Sorry: 對不起 (Duì bù qǐ) — for serious mistakes

Excuse me: 不好意思 (Bù hǎo yì si) — for getting someone's attention, bumping into someone, or minor apologies

Goodbye: 再見 (Zài jiàn)

Okay / Fine: 好的 (Hǎo de)

Navigation & Direction

May I ask...: 請問 (Qǐng wèn) — use this before any question

Where is the toilet?: 廁所在哪裡？ (Cè suǒ zài nǎ lǐ?)

Where is the [Station/Hotel]?: [...] 在哪裡？ ([place name] zài nǎ lǐ?)

I want to go to [this place]: 我要去 [...] (Wǒ yào qù [place name])

Where is the MRT station? 捷運站在哪裡？(Jié yùn zhàn zài nǎ lǐ?)

Dining & Shopping

How much is this?: 這個多少錢？ (Zhè ge duō shǎo qián?)

Too expensive: 太貴了 (Tài guì le)

I want this: 我要這個 (Wǒ yào zhè ge)

I don't want it: 不用 (bú yong)

Delicious: 好吃 (Hǎo chī)

Communication Helpers

I don't understand: 我聽不懂 (Wǒ tīng bù dǒng)

Do you speak English?: 你會說英文嗎？ (Nǐ huì shuō Yīng wén ma?)

Please say it again: 請再說一遍 (Qǐng zài shuō yī biàn)

Please speak slowly: 請說慢一點 (Qǐng shuō màn yī diǎn)

Emergency

Help!: 救命！ (Jiù mìng!)

Please help me: 請幫我 (Qǐng bāng wǒ)

I'm lost: 我迷路了 (Wǒ mí lù le)

Generally nodding and pointing and using gestures and basic English will get you by. Google translate will do the rest.