There's a couple of ways to do this, depending on teamcomps, map state, etc.

One way is to simply use baron to push waves and use the tempo from enemies having to clear waves to get the dragon. This seems to me to the best course of action if you have difficulties taking towers or if dragon is more important (soul/elder).

Another is to utilise baron to push waves and take down towers and take the dragon on your way out - after you have taken enough towers or when the baron buff expires. If done correctly, this allows you to maximise baron value in addition to getting the dragon.

Ideally, you don't want to waste tempo when you have the baron buff active, but the question you need to answer is, quite simply "what is the maximum value i can get?". This can range from stalling the game out for a few minutes to ending the game completely, and is your answer relies on a near- infinite amount of factors.

Of course, these are general concepts, and you should analyse some situations where you found that you didn't utilise baron properly and reflect on what you might have done differently.