1) The first goal of developing good cross face pressure is engaging the toes and not resting your feet flat on the mat. This is mainly if your in side control.
2) Hand placement under the opponent’s neck using a ‘Gable Grip” is another important detail! The “Gable Grip” is clasping your hands together palm to palm, without using your thumbs to hold the grip. In the past, I would always hug the person which began to wear on my biceps! This required a lot of arm strength for the larger or squirmy opponents. It’s important to have very little space inside the bend of elbow when hugging the neck. In No-Gi, you can sometimes grab the far side armpit (on the back) to help with control.
3) Shoulder pressure would be the final detail. You really need to stay as relaxed as possible, especially your arm (bicep). I have the debated the difference between cross facing with my palm facing up or palm facing down. The palm up approach… the top player, is curling which uses a lot of muscle if the person on the bottom is trying to escape. The palm down approach allows them to carry most of your body weight, if done properly. I suggest you try them both and get the opinion of your training partner.
It is never too early to start adding a good face to your game. I have worked on this enough now that it is second nature for me to use a strong cross face immediately when I get to side control/ half guard. Then I can work for the pass or look for the submission. Especially as a white/blue belt, it was a great control to give me a second to think as my opponent had to work hard to relieve pressure.
Picture from: http://www.jiujitsupedia.com