200mg or 100mg?
I'm doing a big assignment, and I can't focus at all.
That really depends on the individual.
You could start with 100mg and wait about an hour for the effects to kick in. If you need more potency, just take another 100mg.
I personally take 200mg in the morning and it lasts about 8 hours. Others like to take 100mg in the morning and 100mg in the afternoon.
Just make sure not to take it too late. A 200mg dose makes it almost impossible to sleep for the next 12 hours. Annnnd stay well hydrated or you'll get headaches.