I'm a newbie here. I've been reading a book, Elite Growing. The author says, among many other things, when a plant has three pairs of true leaves, more blue spectrum of light increases chances of females from your seed. High humidity, lower temps, increasing level of N, lowering level of K, low environmental stress, lower hrs of daylight (14 hrs) and soaking seed in Gibberillic acid. Until you can sex clones, all of these things will increase females from regular seed. Sexing your plants will also cause undue stress, thus the reason for using clones. Great book with a lot of awesome info. The author says true females exist in the gene pool, and only stressing plants to the max will reveal them. Indicas are much easier to identify than Sativas.