4) Know when to go to your pup and when to use all of your will-power to refrain.
In regard to bathroom needs, every owner has rushed to a crying pup at night, believing that it was an important step in housebreaking. And this is not to say that it's not; the thing is that it is not about 75% of the time.
If your Yorkie urinated and had a bowel movement in the evening before you put him in his spot for the night, at the very most, he may need to pee. If you do believe that there is a valid reason for taking him out for this, by all means do so. However, take care to make it clear that this is a serious time and not one for play.
Keep lights as low as possible and while it may be hard to fight the urge, do not pat your Yorkie or speak very much. Middle of the night bathrooms trips should be short and to the point, with the pup being rewarded for doing the deed, but then placed right back in his spot afterwards.
Within his playpen, you will have toys, food & water and his bed. In all remaining spaces, have pee pads. Since a pup rarely soils his own belongings, if he needs to go to the bathroom and you do not respond to that call, he will most likely do so on the pads.
Teaching a puppy to self-soothe is an important step. With his set up complete and with all his needs met, feel confident that you do not need to respond to each bark, whine or cry at night. It may seem cruel to ignore a pup. However, if you have him in a pen, on a cozy bed, in a warm room, with toys to keep him busy, food and water, and a companion toy, you can feel good that he has all that he requires.
By staying back and allowing him to learn to seek out what he needs (and again, it's all very close to him), you are teaching him a valuable lesson. And only in this way, will he stop barking or crying and learn to settle himself down to go to sleep.