where should I install the NOS button it should be somewhere convieniet yet good enough for me to be able to keep a good grip on the wheel

 

build it into the steering wheel, it'll cost a bit, but it will look amazing.

You could make two buttons, purge on left and NOS on the right. the buttons could be somewhere you wouldn't usually press.

or you could build them into the actual steering wheel so you don't see them, do you have e-shift on your car? if not you could put them where you would normally have E-Shift.

so you are gettin the Nitrous Express NOS kit? tell us how it is!

 

B - I plan on integrating mine into the shifter ( if I keep the car ) right where my right thumb rests. That's where I had it on my old 'Vette & comes from my days of driving a stick. Sasha's idea of 2 buttons for purging & activation sounds cool but a purge button on a small kit isn't necessary. Generally, once U get the nitrous up to the injection point, it doesn't bleed back off unless U have a leak or don't use it for awhile, IME. If U do the steering wheel, watch out for that airbag!!