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.