I'd check out the Power Drive and Spike threads for some good info on those, dozens of people have talked about how they experience the effects and when they've found is best to take it. No sense re-inventing the wheel here
As for the others: ginko and pircetam tend to be an "all day effect" or long-duration, depending on the person, sort of thing, though you could time it around workouts if you really wanted to. The guarana caffeine is just like coffee, except it doesn't produce the jitters high doses of coffee caffeine tends to in most people. That'd be a pre-workout thing then obviously. Tea has a little caffeine and other good things that tend to help people relax and and focus better. I just steep a bag in a mug of water personally an hour or two removed from a workout, though you may play around with how long you steep it or what type of green tea to optimize it.
Like Cy said about Spike in those threads, dosage is different for everyone. Depends how sensitive you are to stims, how well your particular system digests things, etc. I'd start with the minimum recommended dose on any products you choose to buy and slowly move up a little, finding an optimum dosage for you. Personally, I find about 80mg of the g-caffeine is best for that, but haven't really played around with the others much myself. Broke-ass college student and all
Have a good one,