How far in advance of my period should i start ibuprofen to prevent cramps & how often/much should i take once period starts to keep cramps at bay?

As soon as it starts: Take ibuprofen, 400-600 mg every 4 hours, as soon as your period starts (or even before it starts, if you are regular and can predict this). I recommend continuing this regimen for the first 2 days of your period to keep cramps away.

2-3 days prior: Start Ibuprofen 2-3 days before onset of period and continue for one day after starting. Use this as a guide for future cycles. If not working start a day earlier. If ineffective then, try naprosyn (naproxen).