In most cases, it’s unnecessary to use phrases such as “he knew”, “he thought”, or “he saw” when dealing with your viewpoint character. Just dive right in and say it as it would be going through his or her head. This is something to definitely watch for during your final edit.
For example, instead of saying, “He saw that it had started to snow, covering the mountain peaks in the distance” you can simply say, “It had started to snow, covering the mountain peaks in the distance.” See how simple it is? One advantage is that this helps pull readers in, as if it’s happening to them. Saying he saw/she saw or thought or heard can act as a subtle bump out of the story. Besides, you want to eliminate unnecessary words, anyway, and this is one place to start.