But for the most part the first thing I do is SLAM my forearms in a pinch around his neck and secure his head in my hands (or between my gloves). I press on his neck with my forearms, making it hurt, making it tough for him to breathe. This also gives you control over his neck, which if you pull and torque on it, he'll move with you wherever you pull him. Now, another key principal to a sound clinch is to MOVE YOUR FEET. You never just stand still and keep your feet in the same place. I don't even keep my feet square in the clinch, always one back one forward, almost like a lunge position unless I shoot in close to switch up positions (which I'll elaborate on in a minute). So one leg back, the other forward. Forearms on either side of the neck pinching tight. Now that rear-leg. From as far back as you can you send it into your opponent's body as hard as you can WHILE PULLING FORWARD on the head and neck. This will disrupt it if he tries to block your knee with his forearms. He'll be drawn forward and hopefully mis-calculate the position. You might also land a bit lower that you anticipate. Not so much chest and mid-stomach as waistline, which hurts a shitload more. So you give him a couple of these knees. Now here's where it gets really fun
Hand-grips:
In another thread we discussed wether your fingers should be interlaced or not. If you're 100% sure your opponent is finished if you lock in your clinch, or that he will at least have a nightmare of a time getting free of it, then interlock your fingers. Doing this makes your grip all but iron-clad and your pushing and pulling on his head and neck that much tighter. He'll feel like his head and neck are in a monkey-wrench. But if he figures out to fight out of it, you're going to have to let go immediately.
If you just use the clinch to lead to other things and not necessarily as a reliable finishing technique, then you'd be better-served just to cup your hands either just behind the ears on either side of his head (fingertips or glove-tips near the back of his neck) and hold TIGHT, or place your hands/gloves one-on-top-of-the-other at about the base of the skull.