TIPS you should not candle any sooner than day 7, this will show you good veining and the embryo, plus opening the bator too much lets your humidity go down and your temps.....Just as long as you turn atleast 3 times a day not less then those for a good hatch...turn the eggs morning, noon and night is what I do...turning helps prevent the yolks from settling to one side and also exercises the embryo....I do not have a turner so my eggs lay flat on the wire mesh...big end towards the back of the bator, pointy end towards the front...
Here is a nice site with some pictures of embryo development. Notice how the chick takes up the entire egg minus the air cell at the end of incubation. I've been reading a lot of posts about chicks being to big to hatch, and being in the wrong positions, when in fact everything looks and sounds correct. I think in some cases people are being overly aggressive in helping chicks and need to do some research on incubation before hatching. I know it's hard to wait but I think in many cases more harm than good is being done. Hope this site helps. http://msucares.com/poultry/reproductions/poultry_chicks_embryo.html