I was told when purchasing my bike that I should have a flat foot when I get to the bottom of my stroke and then pull up like I'm wiping stuff off my cleat (I use Speedplays, so this may not be the same for everyone), so on my upstroke my toe is pointed down a little.

Edit: I'm comfortable when I ride, but I don't race, so I might not be the most knowledgeable on this topic, just thought I'd share my experience.