The very basics of OOP

Hi guys,
Now that I’m starting to do everything the object-oriented way, I basically need some help (I’m a massive beginner at all this class design stuff!)

Ok, so when I create a variable in a class, what is the BEST way to use that data in another class? Surely just extending the class all the time can’t be good. Should I be generating all content in just ONE class and then doing…

siteData = new siteData();

In every class that needs to access it?
Also, can someone please explain delegation and the delegate class a bit more to me please!??

Thanks,
Dave