I started open carrying on my 18th birthday. (I'm now 21 and recently got my permit to carry concealed.)
There is no need to have any certificates, but you should know how to use your firearm well.
Be sure to read up on all the laws, such as for prohibited places. Here is a pamphlet I made which summarizes many of the laws:
In Nevada, the definition of a concealed weapon is:
So the gun must be discernible by ordinary observation. However, I wouldn't want to give an officer any room to try and say my gun was concealed."Concealed weapon” means a weapon described in this section that is carried upon a person in such a manner as not to be discernible by ordinary observation.
At 18, you can also purchase a handgun in a face to face private sale here in Nevada, just not from a licensed firearm dealer. Many people will be hesitant to sell a handgun to someone under 21, but I did buy a handgun on one occasion before I turned 21.