John 1:1 literally translated reads: "In beginning was the Word, and the Word was with God, and God was the Word." Here is the breakdown:

"In beginning..."
Notice there is no definite article "the," it does not say, "In the beginning." John uses this phrase because he wants his readers to know exactly which beginning he is talking about. Genesis 1:1 literally translated reads, in both the Hebrew as well as the Greek translation of the text (called the Septuagint), "In beginning God(s) He created the heavens and the earth." Here again there is no definite article "the" in the text. John is quoting this opening phrase from Genesis 1:1 so his readers will know and identify what beginning he is talking about, that is, the beginning of the creation of the physical universe.

"...was..."
This verb means to exist. It is in the Imperfect Tense which indicates continuous action in past time.

"...the Word..."
Word is translated from the Greek word Logos. From the Greek word Logos comes logistics, logic, etc. The Greek philosophers at that time believed the God of the universe thought of the design for everything in His mind first, then spoke it all into existence, therefore the Greeks called God "the Word."

(Notice John 1:14 says, "And the Word became flesh..." In verse 1, it says, "the Word was," which means that at the time of creation the Word was already in existence. In verse 14, when it says, "the Word became flesh," it means the Word has always been but became flesh (human) at one point in time and history.)

"...and the Word was with God..."
Here the word translated with in the English translation is not the preposition with as in to accompany someone. This with comes from the Greek word pros, which means to or toward, and makes up part of the Greek word prosopon, which means face. When it says "to God" in this text it means face-to-face with God and indicates equality with God.

"...and God was the Word."
Notice the exact wording, it does not say, "and the Word was God," but rather "and God was the Word."

First of all, there is NO indefinite article "a" in Greek so it cannot be translated "a God."
Secondly, it is very important to understand the exact wording used here. In this phrase there is no definite article "the" that goes with the word "God" so some translators insert the word "a" into the text. This is stricly a personal choice for an English translation and has nothing to do with Greek or the original languages.
John purposely did not put the definite article with God. In New Testament times there was a Gnostic doctrine being taught that said, "The God was in the Word" which in Greek meant all that God is was in the Word when He became flesh. This doctrine was not only teaching that all of God was in Christ, but that God was only in Christ and nowhere else. Sabel (a teacher of this doctrine) taught that indeed Christ was all God, but was limited to being just in Christ (the Word) and nowhere else. John did not use the definite article with God because he was refuting this doctrine, which is now known as Sabellianism.

In Greek when you do not use the definite article in a predicate nominative phrase such as this, it expresses a quality, nature or characteristic of the subject you are talking about. John purposely omitted the definite article in order to say that God in His nature and quality was in Christ when He became the Word, but was everywhere else at the same time.

In summary, this verse says:
In beginning, at the time of the creation of the physical universe, the Word already existed and was equal to God, and God, in His nature and quality, was the Word.