If you just throw it in whole, you'll poop most of it right back out....
Grind it up fine with a coffee grinder or food processor, then you can incorporate it into most anything.
I put some ground flax in a glass of water and let it swell up a bit, put in some cranberry or blueberry juice for flavor, and drink it down as a meal replacement. (optional additions are hemp protein powder, greens powder, chia seed)
The bulk of the hydrated flax seed makes you feel 'full'.