sometimes residual starsan in the bottle can make it foam over the top if you are slow to remove the bottling wand.
on my last batch my old friend Bottling Wand cracked on trying to remove the hose. had it for 5 years.. sad. got a replacement coming today i think.
i always get every last drop possible into a bottle. my last bottle is usually more trub than beer but i let it go without priming sugar. i stick it in the fridge and i can get more beer that way. flat, but who cares? did i mention i'm notoriously cheap?