I'm guessing you're familiar with FOIL - how to multiply two binomials. Factoring is just reversing that process. Set up two "blank" binomials.
( )( ). How would each one begin?
(b )(b ) The reason is that you want the F part of the product to be b^2.
How would the binomials end? You want the L part of the product to be -2c^2.
(b 2c)(b c)
Now figure out the signs in between to create a middle term of +1bc.