Phrases for expressing goodwill
It's good to meet you. (First time only) It's good to see you again. (after the first time)
When someone is arriving
Welcome Welcome back! Come in
Have a nice trip. Have fun Keep in touch.
When someone is leaving
It's been nice talking with you. Have a good/nice day.
Do the best you can. Work hard! Keep up the good work
When someone is Encouragement
Good luck! Good luck on your test!