What are the differences between God and mankind? A lot has been said about man being made in God's image. However, when I once explained this to a Hindu lady, she said "God in man's image or man in God's image, it's all the same", implying that she thought the God of the Bible was just man's projection.

However, I think it would be useful to have some explanation of the "otherness" of God as seen in the Bible. I think that most non-Christians are unaware that the Bible has a particular view of God, that is different from their own. It would be nice to have some discussion on the question of the otherness of God.
The statement that your quoted from the Hindu believer has a Pantheistic notion in it. Contrast this with the way the Christian Holy Bible consistently teaches about God and His plan for humanity.


God is distinctly declared as the Creator of Heaven and Earth and the first human being. The account of the creation of the world starting from Genesis 1:1 would be a good starting point.
The names ascribed to God in the ancient Hebrew traditions (Old Testament) would be another field of study that can profoundly improve our understanding on the observable attributes of God that His chosen people ascribed to Him.
God reveals Himself in three persons, co-equal, co-eternal (the concept of Trinity) in order to carry out the plan of Salvation. 
And lastly, and most pertinent when discussing Christianity with people of different faiths, is the fact that the Christian Bible is not a collection of wisdoms, it is not a collection of legends, it is not a collection of legalistic rules and regulations.  Instead, it use all those to weave a coherent blueprint and a model on how to connect ourselves to God, so we can participate in His plan using His strength.  This plan has a definite beginning, and it has a definite end.  It is not an cycle with indefinite number of iterations.


Of course, this doesn't even began to describe how rich the revelation of God in the Scriptures really is. This is just a starting point, a frame of mind to start a discussion.