Tips for using manual focus?

I've recently purchased the nikkor 50mm f/1.8g lens for my entry level dslr (dx format) i have been having a lot of fun with it but i'm just having such a hard time with the manual focus. For ex. Today i took some family pictures for a good friend. Just messing around getting more expirience. And about half of my photos were out of focus when i was using manual focus. She has two infants and the dog came so it was definitely tough to focus fast because they were everywhere. But is there anything i can do to help me focus in on my subjects faster? Auto focus almost never focuses on what i want it to be focusing on!

If possible, use the largest f-stop that the light will allow (without making your shutter speed too slow).

People recommend focusing on the eyes of your subject.

Try to prefocus if possible (so that all you have to do is snap the shutter when the time is right)

Try not to spazz out (usually fuzzy pictures are due to camera shake and not to the lens being out of focus). Rather than running all over the place trying to keep up with your subjects, sometimes it's easier to let them come to you.