Lucky (ラッキー)

Often in Japanese dramas I heard the word "Lucky" (ラッキー) being used. This is the direct use of the English word "lucky", and is usually used to express surprise at one's good luck. 超(ちょう)ラッキー means super lucky.

To express good luck in other ways, we can use こううん/幸運 or うんがよい/運が良い.

To wish someone good luck before an exam or competition, がんばって/頑張って is often used although it does not directly translate to "good luck".
Example:
明日の試験頑張ってね = Good luck in your exam tomorrow
(The literal translation of this sentence is "Work hard in your exam tomorrow")

Another way to wish someone good luck is to use うまくいく. This means "things go smoothly". Example:
新しい学校で、うまくいくといいね = Good luck in your new school
(The literal translation of this sentence is "It would be great if things go well in your new school")

To really include "good luck" in your wish, こううんをいのる/幸運を祈る can be used, but I think this is more formal and is seldom used in conversation.