Please, thank you, sorry — the words that keep you polite.

• Пожалуйстаpozhaluystaplease; you're welcome (also used when handing something over)
• Спасибоspasibothank you
• Большое спасибоbol'shoye spasibothank you very much
• Не за чтоne za chtoyou're welcome; don't mention it
• Извинитеizviniteexcuse me; sorry (polite/formal)
• Проститеprostitesorry; forgive me; excuse me (polite)
• Прошу прощенияproshu proshcheniyaI beg your pardon; I'm sorry (formal)
• Даdayes
• Нетnetno
• Может бытьmozhet byt'maybe; perhaps
• Конечноkonechnoof course; certainly
• Здравствуйтеzdravstvuytehello (polite/formal)
• До свиданияdo svidaniyagoodbye
• Будьте добрыbud'te dobrybe so kind; please (polite request, lit. 'be kind')
• Хорошоkhoroshookay; good; all right
• С удовольствиемs udovol'stviyemwith pleasure; gladly