I have always been taught to talk to God like he's your best friend, I believe He wants us to be open and honest with Him, not strict and formal with all the titles and "flowery" descriptions and names. But it is a personal choice too. I would just pray and say something like" God, what do you want me to call you ?" To Christians , He should not be looked at as a "fearsome judge" as you mentioned, He's a loving , caring, just God who has saved us from the wages of our sins, not this huge ruler whos waiting to stike someone down with a bolt of lightening as some people like to imagine! I hope this helps you !