Just thought to quickly summarize this article (
http://dogstardaily.com/blogs/when-dogs-ask-why ) regarding teaching your dog why its relevant to do something when told.
Doing the above is what really constitutes a trained dog. There's the first step of teaching your dog to do something (usually done through lure or operant conditioning with a clicker), in other words basically teaching the dog what you expect of him or her. The second step is adding a verbal or visual cue to let the dog know that the specific action is to be done when given a specific word/hand motion. And lastly as the author explains a little more in depth is teaching the dog WHY he has to do that when told to do so.
A good example used in the link above is teaching a dog to sit. Rather easy right? Step 1: Hold a treat up over its head to get the dog to sit. Do this over and over again. Step 2: Attach a word as the dog does the action for the association to stick. Step 3: Teaching a dog to sit while visitors come in
because if the dog does this then the visitors will give you attention AND you won't be yelled at or sent to another room. (Of course this is done a little more differently when clicker training).
Remember that a dog doesn't come to us WANTING to do everything we ask, it has natural instincts, so we have to 'override' these instincts and learn to teach a dog that there is a reason for what we ask. So before going on about training take a quick moment to meditate and ask yourself Why you want the dog to do this, and of course "because I told you so" doesn't count.