Those tips

Sorry about the no post yesterday. Got caught up with work. So as I promised some tips for Pokémon X based on my experience. That's not to say my tips can't be used in Y, it's just that I don't have any experience with how the game play might be different. I would assume not much. So I'll try to go in chronological order, but if I go back don't be shocked.
-There is currently a mystery gift promotion going from now until January 15th. You get a free Torchic with Blazikenite which will allow Blaziken to megaevolve. This is a must because you can't find this megastone in the game. Plus you get a free Torchic.
-Base your starter off the fact that you will get one of the Kanto starters (Bulbasaur, Squirtle, Charmander). So if you want to get Charmander then you probably shouldn't get Fennekin. Especially if you plan on training a Fletchling who will gain the fire type once it evolves, plus you will have a free Torchic. I planned on getting Bulbasaur to counter my rival since I know she would have the water starter so I got Fennekin. I didn't plan on training Torchic.
-Your first gym leader loves Bug types. That means Chespin won't be your star player. You will be able to get Pidgey and Flechling and even a Pansear before you make it there. Her pokemon are also at 10 and 12 so keep that in mind
-You will find a Snorlax pretty early on in the game at lvl 15. This is a major plus. It doesn't know Rest so it won't regain health and can be a major power house on your team.
-The HMs in this game are more for getting you items or making shortcuts. You will briefly need to use surf and strength will make it so you don't have to go all the way around in a cave. Both of which will be a must in Victory Road however.
-Exp share is your friend. Once you get it after your first gym battle you won't have to grind anymore if you take the opportunity to battle as many trainers as you can. You'll find your pokemon will stay at around the same level this way.
-Catch a Honedge. I can not stress this one enough. It is such a trump card in this game. It has a very diverse movepool. It knows Fury Cutter when you find it (which had it's power upped) and learns moves like Iron Head (which fairy types are weak against), shadow sneak, night slash, aerial ace, and other moves I'm sure I'm forgetting. It's also part ghost so it can be your big trump card against fighting since you can use aerial ace which they are weak against.
-Team Flare likes to use poison, fire, dark, and on rare occasion normal.
-There is a lot to do in Lumiose city. The more you do in that city the more style points you get. Which you can't see of course. The more style you have the more places you can visit and in some cases get a break on prices.
-The first and third gyms don't let you leave to heal your pokemon. Once you are in you have to defeat all the trainers and then beat the gym leader to leave. All other gyms won't force you to stay.
-You will have a long drawn out line of battles to get to your legendary pokemon (Xerneas or Yveltal). Once you face the leader the at the Secret HQ (not to be confused with the base in the café) go heal your pokemon. You will then have a series of 3 double battles (your rival will be your partner). His or her pokemon will heal, yours won't. Go heal again before entering through the doors. You will then have 4 more admins to deal with. Save after you finish. The next step you take towards the core will make the fight begin. Once you've captured your legendary you will then be challenged for the last time by the leader. This time your pokemon will be healed.
-Hordes will happen at random and will feature 5 pokemon at levels lower than the levels of the pokemon you'd normally find. Sometimes they do have hidden abilities. To cause a horde you need to use honey or sweet scent. Hordes will come in handy if you want to catch a pokemon at a lower level to train it to your liking. At a certain point you'll only run into evolved pokemon.
-When you face the Elite Four (I beat them last night 10/16/13) you won't challenge them in a specific order. This time you can pick a room to challenge in any order. The types are Fire, Water, Steel, and Dragon. My advice is to attack Dragon last. Dragon types can be very hardy and you want to have the extra experience to make your fairy or ice type stronger to face them. They all will have pokemon at the exact same level. 3 pokemon at level 63 and one at 65.
-After you become the Champion you will be thrown a parade where you will have one last battle. It's a very easy battle. 3 pokemon (Torkol, Golurk, and Silphyh).

These are just a few of the things that I wish someone would have told me or I noticed. These should make your game go a little smoother to help you require less turning on and off for a do over. If I think of anymore I'll post them.