How can I maximize the caffeine content of my coffee?

Use lighter roast coffee: caffeine burns off as the roast darkens. All other things equal, though, the stronger the cup of coffee, the more caffeine will be in it. You aren't going to reach caffeine saturation just by brewing (even very) strong coffee. So brew coffee with lighter roasted beans to your maximum desired strength.

1. Start with a bean with more naturally-occurring caffeine.

   Colombia Excelso 1.37%
   Colombia Supremo 1.37%
   Indian Mysore 1.37%
   

2. Prepare the coffee in a manner that produces the most caffeine.

   drip: 1 cup (7 oz, 207 ml) = 115–175 mg.
   brewed: 1 cup (7 oz, 207 ml) = 80–135 mg.
   espresso: 1 shot (1.5–2 oz, 45–60 ml) = 100 mg
   

Taken from http://en.wikipedia.org/wiki/Coffee

If you want to take in twice the amount of caffeine, why can't you just drink twice the amount of coffee? If you start messing with the ratio of bean to water, or trying other tricks, you're likely to just get bad tasting coffee.

If all you are after is caffine I'd just buy some caffine pills, you can get 16 packs here in the UK. If it must be in coffee then dissolve a couple in a normal brew.

However I must say I wouldnt recommend it - overdosing on caffine is bad - especially on a regular basis.

There is liquid caffeine you can add if you're just in it for the caffeine jolt. A capful of 5150 juice is 83mg and is comparatively extremely cheap when weighed against pre-made energy drinks and 5 hour energy.

You can add it directly to the coffee, which will make the coffee much more bitter, or you can take a shot of it and then drink your coffee as normal.

I can say from experience that although I am finding myself more and more immune to coffee, soda, and 5-hour energy, 5150 still works (and works well, and fast). Perhaps it's because so much of the caffeine is absorbed in the mouth.

Without wanting to preach, I wanted to say, as NBenatar mentioned: no matter what route you go, be careful. I also know from experience that caffeine addiction is very bad, and actually makes you significantly more tired. Over time you need the morning caffeine just to reach energy levels that normal people experience without any caffeine. From the second article:

The millions of people who depend on a shot of coffee to kickstart their day are no more alert than those who are not regular coffee drinkers, say researchers.

A cup of coffee, suggests a study, only counteracts the effects of caffeine withdrawal that has built up overnight.

I can say with all honesty, the first week of drastically cutting back my caffeine really sucked, but now I'm more alert in the morning than my colleagues who drink coffee like it's their job...though, we're programmers, so I guess it kind of is their job :)

Buy cheap robusta coffee instead of expensive arabica coffee. Robusta has about twice as much caffeine as arabica. If you're only drinking coffee for the caffeine then buying arabica is a waste of money.

Have you try Yerba Mate tea? It has similar effect as coffee and it is way healthier for you. You could drink more than a cup a day too!

It is believe to have cholesterol lowering properties (along with antiobesity properties) and contains minerals as well.

Having different flavors keeps it interesting too!

You could brew the coffee the night before and let it sit on the warmer over night Only brew about 4 cups should be down around 2 cup ms by morning this in theory should double the concentration of everything

To get the best coffee (and therefore caffeine) ratio to water drink Espresso.