Serious Pokémon trainers understand the power of breeding, and if you want lots of Pokémon in Brilliant Diamond and Shining Pearl, you'll need to embrace this mechanic. At the heart of the breeding concept are the eggs that you will have to try to hatch.
In order for the eggs to hatch, you need to travel with them and there are ways to hatch things in your favor so that you can hatch the eggs faster.
How to quickly hatch eggs in Brilliant Diamond and Brilliant Pearl
Eggs hatch based on how many steps you take, so traveling as much as possible is the simplest thing. Spend time on the go and you'll get close to hatching eggs too. You can also use Pokémon on your team to heat eggs. You must look for Pokémon that have the Fire Body or Magmatic Armor abilities.
If you have a Pokémon Flame Body or Magma Armor on your team, you will cut the hatching requirement in half. Some good Pokémon to look for are Magmar and Ponyta for Flame Body and Camerupt and Magcargo for Magma Armor.
Magmar will evolve from Magby, while Ponyta is found along Route 206 south of Eternia City and north of Oreburgh City. Camerupt can be found along Route 227 or evolved from Numel, while Magcargo can be evolved from Slugma or encountered at Stark Mountain.