I have the Harris Speed Works 2v plate kit on my car and I love it. The plate setup makes things a lot easier/cleaner to install.
Most kits are activated off a WOT (wide open throttle) switch, so when the system is armed, all you have to do is mat the gas and it'll activate the nitrous.
I'd personally suggest a wet kit. On a 100 shot, you can get away with a stock fuel pump, injectors, and tune providing that your fuel pump is in good working condition, you keep a clean fuel filter, and none of your injectors are clogged. Wet kits rely on fuel from the rail, which is fed into the fuel solenoid and then mixed in with the nitrous at the nozzle (or plate) when the system activates.
A dry kit is a nitrous-only delivery, and the additional fuel required relies on a fuel system which has been modified to handle the demand for additional fuel (as in, a stronger fuel pump, injectors, and a tune are a must).
NEVER run nitrous on a performance tune (as d98gt said), as the timing advance will cause detonation and destroy the engine. You can run up to a 100 shot on stock timing, but it's HIGHLY recommended to pull at least 2* for a 100 shot, 4* being ideal. I have pulled approximately 2* and all is fine.
A window switch basically creates a window of activation for your nitrous. The most common application is setting the nitrous to activate at 3k, and shutting it off at 6k. This prevents the system from activating before intake velocity is high enough to carry the nitrous and fuel mixture, thus creating the possibility for fuel puddling in the intake manifold and a nasty backfire. It also protects against over-revving the engine, such as if/when you miss a shift.
As far as plate kits; I prefer them over nozzles. Direct port is best, but also a whole different league in terms of installation and cost. Plate kits for 2v's sit between the upper plenum and intake manifold. The nitrous and fuel mixture (assuming a wet kit) has a direct shot into the intake manifold and is able to atomize (mix and disperse) more efficiently and evenly when compared to a nozzle kit (which sits 4-6" in front of the throttle body, potentially passing the last bend in the air intake, then passing through the throttle body, and finally making the abrupt bend in the upper plenum before reaching the intake manifold). Installation doesn't require you to cut a hole in your intake, and there is zero concern of a nozzle backing out/blowing out and spraying nitrous/fuel under the hood and potentially creating a fire.
As far as other notes... you'll need 1 step colder spark plugs for a 100 shot. I use Autolite 103's if I remember correctly. I suggest copper plugs. Nitrous will wear plugs faster, thus you'll need to change them more often. Copper plugs are cheap. I believe nitrous has an adverse chemical reaction with either platinum or iridium plugs as well, so that's another reason to just use coppers.
You'll need to gap the plugs down as well, just as on a boosted car. .034 is the recommendation, but I installed a new set at .040 or so to help with regular driving and I haven't had any spark blow-out.
Depending on your location, it can be cheap or expensive as hell to fill the bottle. I pay $3.25 a pound, but have talked to others in different parts of the country that pay $5-$7 per pound.
A 10lb bottle will last 7-8 1/4 mile passes on a 100 shot before the pressure starts to drop too low to be beneficial.
NEVER USE A TORCH TO HEAT THE BOTTLE! Yes, people do this, yes there's a "proper" way to do it, but just avoid it all together. The bottles are under IMMENSE pressure (sitting in a car on a summer day, not uncommon to peg a gauge at 1500psi). You do not, under any circumstances, want to weaken a spot on the bottle with a blowtorch. Bottle heaters are relatively affordable (around $100 for a decent one) and will help keep an even pressure in the bottle, which will keep your passes consistent.
You don't "need" a purge kit. They are handy, and look cool... but you can bleed the line at the solenoid and achieve the same results for free.
Don't tamper with/remove the burst disc. They're there to release the contents of the bottle in case the bottle over-pressurizes to the point where it could fail. I've heard of people doing that, but I don't know why.
Hope that helps.
