When you catch lots of Dittos, you will have all sorts of Natures, from which you can select for breeding the nature you want. And, you may even encounter some with perfect IV, those will be used for breeding perfect IV. Breeding competitively can be very complex.

Everstone will give 50% of chance to pass down the desired Nature.

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About soft-reset breeding, this is what we do in Gen 4(Platinum, DP, HGSS). I'm not sure if it's still the same in Gen 5 since I've not bred anything yet in BW.
1) Put the parents with the respective items together in Daycare, (Everstone, Power Items like Power Anklet, Power Weight, ect.)

2) Wait for phone call, then SAVE near the Daycare man, after you have saved, receive the egg and hatch it!

3) Check the Nature, Gender and Ability. These 3 characteristics will remain after you have saved before receiving the egg!

4) If it's not any of the 3 characteristics you want, you can either keep the baby or soft-reset(L+R+START+SELECT), then reject the egg and wait for another phone call. Repeat this until you get the desired Nature, Gender and Ability.

5) After you have hatched the egg with all the characteristics you want, it's time to go for IV! This is when you soft-reset mindlessly until you get a Pokemon with OUTSTANDING ability. Again, all the 3 characteristics will remain, the only thing that will change is the IV. You can check it in-game by talking to an IV guy. He's in Nimbasa City, Gear Station, according to Serebii.net. In HGSS, the IV guy is in Battle Tower.

Anyway, you need some Pokemons with 31 IV first before going for the IV breeding. Everstone will get the nature you want pretty easily. So, the main point is to save in front of the Daycare man before receiving the egg. I feel bad to hatch countless numbers of the same Pokemons and put them to sleep in the PC. That's evil!

Edit: put a Pokemon with Flame Body ability in your party to half the hatching steps, Pokemons like Slugma. Breeding IV requires luck when hunting for Dittos. That sucks. Alternatively, you can ask for Pokemons with 31 IV in the stats that you want through trades, it doesn't matter if it's male or female. Just don't ask for too unreal ones, those might be hacked or clones.

who have lvl 1 bagon? want to train it from start but i don't really have anything to offer~

I've been thinking of making a team consist of Salamence, Toxicroak, Snorlax, Darmanitan, Zoroark and Cloyster wht do you guys think?

Another thing, being Alert to Sounds may not always be 31 IV, it can be less than that, you must check the parent with such characteristic first with the IV man before putting on Power Anklet and throw into the Daycare.

Have you bred one with 31 IV already?
This ^ 31 IV is only important for speed and attack/special attack stat. There are many perfectionists out there who wants very good IV. My Pokemons must have at least 2 maxed IV and the overall potential must be Outstanding, so that it can take hits better. I'm more like a breeder than a trainer.

guys when checking the IV at the battle subway, ok before he told you about the possible IV your pokemon has, when he say decent, relatively superior and etc.
how does it effect your pokemon?
btw if a pokemon by breeding, it says get along well but play w/ other pokemon more, meaning not at all will give out eggs?

Zoroark is never good for competitive play in the first place...

It's called soft-resetting for me, it's pretty easy once you understand how it works. With this method, you can retain the Nature, Ability and Gender that you want, ALL THE TIME! then soft-reset until it gets Outstanding potential and max IVs.

@xShinji, a Power Item with Everstone is really the best way of breeding good babies. I tried with both Power Items alone before and it sucks.

Relatively Superior and Outstanding with 3 Maxed IVs,... hard to settle down.