Where to begin... firstly, when dealing with non-feminised
single strain seed in a high quality neutral pH growing medium with a balanced nutrient/mineral load, water to spare and sown outdoors late spring early summer the male/female ratio is roughly 50-50, give or take. Of course, parentage has a lot to do with these numbers.
In nearly 40 years of growing from 10's to a hundred at a time I've found that males tend to shoot ahead of females in the early vegetative stages. They almost always present with longer internodes, bigger leaves and generally sparser frames. Knowing this is a bonus and saves time otherwise wasted growing males that can be replaced with potentially female seedling to fill the gaps. Males are also nutrient pigs and really hoover it up to beat their mates to mature first and pollinate any flowering females in the vicinity; nature's way of passing that individual's genes on to the next generation. With the odd exception for breeding needs I 'rogue' these out and have very rarely ended up with a sneaky male hiding among the girls. Males also tend to declare earlier than females, although as Wise420 posted, stress can also lead to early declaration. Again, in my experience these tend to be staminate first rather than pistillate. Stable strains producing predominantly females occassionally sprout a male flower here and there to satisfy their need to breed in the absence of male plants. The resulting seed will almost invariably produce plants of the female persuasion

. Less stable var's or those with hermaphroditism in their genes can produce many more male flowers and really screw a breeding program.
Then there is pH. Aim for a slightly alkaline pH if you want more females. Dressing out with wood ash or good old Potato E helps here. Boys tend to really boom in more acidic nitrogen-rich soil types, typically where you would find broad-leafed grasses, like around effluent drains, for example.
In the end, enough is known about cannabis botany today to make informed choices about how you deal with this weed in cultivation. Kings are ok for dilletantes, but in the end it's Queens you really want. Hope my ramble helped out.