This is how I play: I bolt through the game as fast as I can the first time around, doing as little extra as possible to get all the badges and HM's, I then take a more leisurely stroll back across the whole region with all the HM's in pocket to access all the hidden TM's, items and pokemon I missed. I do this now as I had a bad habit of wasting good TM's on Pokemon that I lose interest in eventually, So now, no TM's till before the elite 4. Also before the elite 4 though I like to catch any legendaries that are available, Fight through the Elite 4, the Champ then go after the remaining legendaries.
I have started a new trend also in the 4th gen games, I restart the game 3 times before begining to put the 3 starters onto another game so that once a I can trade I can play with all three starters for that region.
Then after the whole region is explored I get into filling up the pokedex and finally the Battle frontier.
Zeus