Find an Ancient Greek course open to the public by researching religion and classics departments of universities. Contact the school's administration to see if you would be eligible to take a course, if you are not currently enrolled at the school.
Choose your text books, if you've decided to learn the language alone. Websites like The Institute of Biblical Greek and Learn Ancient Greek can help you with letters, sounds and grammar.
Learn the alphabet first. Master the sound of each letter before you delve into words.
Study vocabulary, specifically words that come up often in Greek language such as names of gods or famous places. Quiz yourself until you can master reading the words in the original lettering and connect them to the vocabulary.
Learn a few verbs before you begin grammar lessons to ensure you will be able to understand simple sentences.
Do all work required of you, if you're in a class.
Practice writing and reading texts as much as possible to get your mind used to the difference in letters, sentence structure and styles.