In this Mode It is surounded by the Key of D, So D is the start in the Circle of 5th's.

It has a flat 3rd and a flat 7th from the Natural Major Scale

[G Dorian Asscending and Descending]

e|---------------------------1-3--3-1-----------------------------------------|
B|----------------------3-5-----------5-3-------------------------------------|
G|----------------2-3-5--------------------5-3-2------------------------------|
D|----------2-3-5--------------------------------5-3-2------------------------|
A|------3-5-------------------------------------------5-3---------------------|
E|3-5-6---------------------------------------------------6-5-3---------------|