Nitrous

This is in my opinion the easiest to install, and probably one of the easier systems to tune. Install for a basic plate or single nozzle system on average is about 4 hours, and has instant results, but start low and work your way up. Nitrous has received it's bad name from too many people throwing a system in their cars, putting the largest jet(s) in they can and going, this is a sure way to get poor results and usually ends up damaging something.
General rules of thumb (but not exact science) are: retard timing 2 degrees for every 50 HP increase in "shot"
I.E. a 50 shot would need 2 degrees of timing retard, when "spraying". a 150 shot would need 6 degrees of timing retard, since: 150/50=3 3x2=6, that easy. Some engines (combinations) may require more or less retard for the same size shot, but this is where tuning for maximum power comes in.
A HP "shot" on a stock engine (with cast pistons) should not exceed 50% of max total rated power.
I.E. Engine rated at 180HP 180/2=90, again this will have to be determined for each engine, I know some people have not been able to run more than about 30% without having problems, others have been able to run as much as 75% and have great success.
Never spray at under 3000 RPM and have the nitrous stop spraying BEFORE the rev limiter, this is where "window switches" that read RPM are a great asset.
Only spray at WOT, there is no need to spray before this point as you just need to push down on the pedal more if you want more power (RPM). Really why would you need any sort of added power at anything less than WOT?
It is also a great asset to know what kind of limiters are on your vehicle, such as a spark cut limiter or a fuel cut limiter. As far as I know, all 660s use a fuel cut for both RPM and speed limiter, which makes running on nitrous at above these RPM's and speeds very touchy and should not be attempted, since the biggest reason for bowing an engine is running lean, which a fuel cut will do.
More info can be found on manufacturer sites.

Turbocharger

I find this to be the second easiest to install, especially in a custom form, where no kit is available for your engine and vehicle. The reason I say this, is because you can in most cases with the 660, use the crossover pipe that runs over the transmission to attach a turbo to for exhaust power (exhaust force) to drive the turbine, there is no specific location for mounting the turbocharger, but a few things do need to be taken into consideration:

Mounting location: Should be away from flammable objects as the turbine housing can reach extreme temperatures, a lot of times in the 1200*F range. Usually a turbine shield is used to control this heat from burning other objects and also to help keep the heat in the turbine. Mounting angle: The oil feed/drain orientation should not exceed 30% off a vertical axis, this promotes oil drain back into the engine and keeps oil from pooling in the bearing housing.
Mounting height: Should be as high as possible to promote oil drain back to the engine, without the need for a scavenge system, as that adds more cost and should only be considered if it is the only possible way to get the oil out of the turbo and back in the engine due to a necessity of low mounting height. It is usually recommended that the bearing housing be approximately the height of the exhaust ports of an engine like the 660 where the heads are high (as compared to a "boxer style" engine). Higher is good.
Oil feed: Should be at least 1/4" and made of a good hose, I recommend nothing less than stainless Braided, like Earls, Aeroquip and Russel supply, this assures a consistent pressure and less likely to chafe. Oil drain back: Should be at least 5/8" in diameter as the oil coming back out of the bearing housing is usually quite frothy and will not flow well through a small hose. The fitting in the oil pan (most used and usually most convenient) is to be above the oil level when the engine is running, and again is due to the oil being frothy and helps drain the bearing housing instead of backing up the froth that is draining back.
Exhaust (from head to turbine): Should be kept as a good balance between small and able to flow enough, meaning that exhaust velocity is something that is needed to help spool the turbo, but not so small that it chokes the engine at higher RPM. Usually if 2 tube/pipe sizes are being considered, the smaller one generally works best. Exhaust (from turbine outlet): should be as large as possible to promote quick exit of the exhaust gasses, this helps promote quick spool times and since the exhaust gasses have already done their work at the turbine it is not necessary to observe any sort of back pressure benefits after the turbine, since the turbine itself does act like a restriction.
Intake piping: should be a sufficient size to flow enough CFM to support the power level desired, be kept as short as possible, but also kept on the small(ish) side, this will promote quick pressurization of the intake and also keep heat soak to a minimum. Intercoolers: Covered later.

Supercharger

This in my opinion is one of the more difficult systems to install in a custom set-up. The reason I say this, is belt alignment is paramount, when a belt is spinning at several thousand RPM, it really does not take much for it to get thrown or "spit" off the pulleys. The supercharger also needs to be mounted in a very solid fashion, again due to high RPM, since if the supercharger were to be pulled by the belt, seeing as when it creates pressure this places a load, it can spit a belt this way. There have been many (DIY) systems where at high RPM no load tests, the belt stays on, but placed under load (vehicle accelleration tests), when the load of creating pressure is placed on the supercharger with a weak bracket system, it flexes towards the crank and spits the belt, a strong bracket system is needed.
A lot of other general ideas can also be taken from what is needed with turbocharging, mounting high, oil feed and drain back (if it is an external oiling supercharger) intake piping, mounting angle, etc.

Intercooling

There are many opinions and ways of doing this, generally for a front mount air to air intercooler, a larger area is desired, with large tubes, but there is a balance between too large of a tube and too small. Too small and the IC will be a restriction, too large and there will not be enough surface area for each tube to effectively cool the intake charge. End tank design is also to be considered, a nice flowing (smooth transition) end tank is desired, since it will be less turbulent and help promote flow through the IC core(s). For an air to water IC, there is a lot to this subject and would require a lot of space and time to cover all of the general ideas, and should only be considered if ample cooling from an air to air design is not available, such as very little vehicle frontal area where an air to air IC couldn't fit, vehicle design, where the intake tubes from the turbo/supercharger to the IC and from the IC to the TB will be be quite long or nearly impossible to actually run through the vehicle.

A couple books I'd recommend reading would be:

Maximum Boost Author: Corky Bell
Turbochargers Author: Hugh McGinnes Distributer: HP Books