Confession is good for the soul and I must confess I have not kept up with my Greek as I should have after two semesters of Greek in college and one in seminary. I am thankful for resources like Greek for Everyone by A Chawick Thornhill.
Chadwick covers the basics of New Testament Greek in such a way that would make this book accessible to even a laymen. I he gives some of the most important advice on progressing and maintaining use of language in his first chapter. Chadwick in addition to providing a suitable foundation for understanding the basic vocabulary and grammar of Koine Greek also provides valuable insight into interpretation and application.
If you are a teacher of the word, especially if you are a pastor, I would encourage you to maintain your study of the original languages. If you have no background in Koine Greek this resource will serve as a guide to get you going and point you to further resources as you grow in the languages.
Disclosure: I received a copy of the book from the publisher for the purpose of reviewing it. The opinions I have expressed are my own, and I was not required to write a positive review.