What is the earliest point at which I can determine the sex of a plant? Will I need a magnifying glass to be able to tell the difference between the balls and pistils?
Prolly around week 5 of veg or thereabouts you'll start to see pre-flowers. A magnifying glass is nice but not necessary (unless you have crap eyes like me ).
What exactly will pre-flowers look like? Some tips for any sort of sex identification would be nice as well, leaf formation, smell etc.?
I think it's more like week 6-8 if you're gonna stay in veg cycle otherwise, you can put them in 12/12 cycle start showing sex within a few weeks.
Leaf and smell won't tell sex. Take a look at the pic above. Soon you will see a little 'bud' starting to grow where the branches meet the stem. The little bud could be either a) a female calyx or b} a male pollen sack. The key is to keep an eye on that bud. If other buds grows next to the first, then that's a male - toss it. If two tiny white hairs grow from the 'bud', then it's a female - keep it. GL! Edit: Soapman stole my pic thunder!
I often spot female pre-flowers without any kind of magnifying glass as early as 3.5-4 weeks of veg on 18/6. That little white pistol is very distinctive when it starts to poke out.