Don't be afraid of Nitrous. Properly used,it is great. Abuse it and you will be walking home with a blown motor.
Learn all that you can before getting a kit,some people should use something other than Nitrous to attain their goals.
Read the manual carefully when you buy a kit.
Fuel is the most important commodity in your engine,make sure you have enough.
Make sure your ignition system is strong.
Make sure you set the timing to the reccommended settings as stated by the Nitrous kit manufacturer.
Find a place local to you that offers Nitrous refills for a fair price.
Get the proper permits in order to use Nitrous Oxide in your car.
Since Nitrous will make your car go faster in the quarter mile,you must gear the car for nitrous use,not for the motor only.
Direct Port System
Direct port systems are the most accurate in fuel and Nitrous metering,are the most expensive,require heavy fabrication/modification,and are not easily hidden. Direct port systems put both a fuel and Nitrous line to each intake runner on an engine. Since each runner is individually tuneable,equality can easily exist between cylinders. To do this,each cylinder needs both a Nitrous and Fuel line run it-8 fuel and 8 Nitrous-all bent and installed precisely. It is obvious you should either take the intake off the car first,or better yet,have a pro do it. The kits also are expensive,starting at $700,not including pro intallation. These kits are the safest and most powerful when using Nitrous Oxide. Kits add from 200 to 500+ extra hp.