In my writing, I find that foreshadowing comes naturally even if I don't know exactly what it is that I will be writing down the road...and I do it through memories.
Some will say that flashbacks are not effective in fiction, that it takes the reader out of the story, but I think if it is done well, and is a brief memory, it not only adds to the story and advances the plot, it can deepen the understanding that the reader has of the decisions being made by the main character.
Example from my current work in progress:
"Saturdays had always been the day she cleaned and that ceiling fan had been the one household appliance that she always needed help with for one reason or another. When the switch on the wall wouldn’t work anymore, my dad’s brother, the one we called only by “Uncle,” had come over and taken care of it for us without charging my mom a dime. The time my sister did a cartwheel in the living room and broke one of the blades with her foot, Sears delivered a new set of four blades to our door and we replaced the white blades with ones that looked like wood. Pastor Timothy had helped me change them out and my mom had made shepherd’s pie for him to take as a thank you. Staring up into the spiraling brown, I remembered that she had left out the carrots as if she’d known that he didn’t like them."
(this is a memory the son is having after the death of his mother...as he is trying to piece together the life that he didn't know his mother had)
This paragraph, standing alone, could almost be the start of a story but, as placed in my current novel, the flashback, albeit brief, serves a purpose in advancing the plot and foreshadowing what is to come. I don't believe that one set of ideas about writing covers all novels and for that reason, I will adhere to my belief that flashbacks can work in small doses.