Well, you havnt really given much information to work with.
What types of moulds are you familiar with (plastic, aluminium, rubber, etc...)
The most basic moulds are probably gravity moulds for cast aluminium, so that would be a good place to start.
But as most toolmakers would tell you if you have no experience with tools your best to decide what type of mould you want to make, then go to a factory that uses them and study them.
Or, just hire a toolmaker that knows what he's doing.