Diphthongs —The diphthong is composed of two vowels, but produces one sound. These are basically the same as their English counterpart.
Breathing Marks —The breathing mark is used with all words beginning with either a vowel or a diphthong. When the smooth breathing mark is used, the vowel sound is pronounced normally. When the rough breathing mark is present, the vowel or diphthong will sound as if an "h" precedes it. For example, the diphthong "ai" will sound like "hai". To distinguish between the two, notice the curve. The smooth breathing mark curves to the left. Whereas the rough breathing mark curves to the right.
Punctuation —There are only a few punctuation marks used in the Koine Greek. It is essential that one understand how sentances are constructed and what marks are used. Besides the above marks, there are certain accents, which are also used. While I have not included them here, it should be known that knowledge of them will help a little with pronunciation.
Double Gamma gg —This double consanant is not pronounced as "g" "g", or even as a harsh "g". Instead, it is pronounced with an "ng" sound as in "angel" or "evangelism".