Initial stages of creating a game

[Jostain]

when you envision the game, what kind of game is it? does it look like early final fantasy with turned based combat or does it look like skyrim? or is it a visual novel/dating sim?
These hava huge differences in terms of scope and requirements that one needs to know this before giving any kind of advice.

[Robo4900]

If you're mostly talking about storyboarding cutscenes -- or any other type of scripted sequence -- writing some of those out in script form should work nicely. But really, any method you're comfortable with should work; ultimately, as long as you're understood, it'll do.

If you want advice any more specific than that(Particularly that which refers to gameplay), you'll have to elaborate a little more on the type of game, like Jostain says, but hopefully this should give you a start, at least.