What's the earliest a female begins ovulating and becomes fertile? I think I remember it being 2 weeks before the first period but not sure.

In general, you can expect to ovulate about 12 to 16 days before a period is due. However, some women naturally ovulate a bit sooner and some a bit later. You can also experience an off cycle where you might ovulate far outside what is normal for you or not at all.
This is why, while you may have times in a cycle that on average are safer than others, or times when you are most likely to be fertile, using various methods to determine when you are most likely to ovulate can help increase or decrease the odds of pregnancy.

With regard to the start of menstruation, cycles can often be even less predictable, and ovulation can be irregular.