Completing the look is fairly easy. Start with a t-shirt. Layer with a hoodie. Apply your favorite black leather jacket over the top. When it comes to pairing a hoodie with a leather jacket, in general neutrals will be your best friend. When I lived in NYC, one of my best friends (Jared) favored a bright yellow hoodie. He wore it daily. As nice as he is, it's a terrible look. So don't be a Jared when it comes to this.
Heather grey is a great choice with black leather. Or brown, really. The contrast between the light and dark colors is really striking. It ramps up the visual interest. Black jackets are very versatile and work great, especially if it's a genuine leather jacket. Blues and darker greys are also solid choices. For brown bomber jackets, greens, especially muted or forest greens, can really be effective. But to be honest, I prefer a medium grey with a brown leather jacket.
The general look is to wear the jacket open with the hoodie visible underneath. The hood should always be popped out to show over the back of the collar. Of course, New York and New England's fashion-forward men sometimes legitimately need to zip front of the jacket and put the hood up, too, especially in autumn or colder months. That pragmatism is a great benefit of this look. It's truly effective, both style-wise and for warmth. Remember, thicker, biker-style leather jackets will also be highly effective at repelling rain and snow. Jackets from retailers like LL Bean are also known for being sturdy. If the leather's properly treated, water will bead on it.