Best way to make a concept for a videogame model? Im working on a little videogame with some friends, but we want to learn how to work like pros. I'm the one who does the concept art, and we divide the modeling work between each one of us. This means that I will have to draw concepts that both I and them must look at when creating models. What's a good way of doing concept for videogame characters? Is the orthogonal projection the best or will it be fine with just a pair of sketches? 

Edit: Maybe it will be better to ask this on a design forum rather than here?
I will do my best to answer your question within the bounds of the Blender Stack Exchange focus.

If you've ever seen professional concept art, they often have 3 view of a character/concept object.

-Frontal
-Profile
-close up

This is so the entire concept can be displayed. In blender, the frontal and profile views are often used in character modeling.

A common practice is to enable the "insert images as planes" add-on and place the planes in front of and next to the character you are modeling.

There are many tutorials and examples of this. A quick internet search will probably prove fruitful.

I hope it helps!