Is there a standard way to format a flashback or daydream within a longer narrative?

I personally haven't written anything with flashbacks. However I've read several books in which the author will have a flashback chapter right before a big event. For example: If "the hero" is about to storm the facilty to rescue his/her friends. you might want to create a chapter giving some memorable moments with the hero and his/her friends and why they are so important.

If you want to have it more sporatic (like something you would see in a movie) then you can interject certain parts of your narrative with flashbacks. Example: say character A is in a fight with character B. Character B assumes a very unique fighting stance and immediately character A has a flashback of his old master who taught him this technique. As they fight you can jump back and forth between the present and the past to give the reader that this fight is playing out almost identical to how it did when character A trained with his master.

For daydreaming, I have found that it's quite similar to flashback (in the moment) but its a much smoother/slower transition. Example : "Jenny looked out the window, she loved looking at the clouds, so many shapes and colors. one cloud swirled faster than the others, almost as if it was alive. it continued to do so faster, and faster, until Jenny realized that it wasn't an ordinary cloud but a tornado. As it touched down the sheer force of the wind destoryed everything in sight. cars flew into buildings as it came directly in front of her. A face appeared in the tornado, malevolent and sinister. it spoke to her ' Jenny! are you listening?' Jenny blinked several times, realizing that what she saw was just in her head".

Hope I was able to answer your questions, and continue to hone your craft. I would love to see what you have when you finish it.