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Pokemon Black and White: Breeding Guide
Breeding was originally introduced in Gold and Silver. It is the perfect example of Pokemon being way more complex than it initially leads on. By breeding, you can craft a Pokemon with specific IVs, moves, and natures that would be difficult to find in the wild.

Pokemon breeding requires two Pokemon of opposite gender. Each of those two Pokemon must be in the same egg group in order to breed. The compatible Pokemon need to be dropped off in the Pokemon Day Care. In Black and White, the Day Care is located on Route 3, northwest of Striaton City. The option to drop off two Pokemon at once is only available after the Bicycle is obtained in Nimbasa City. If the two Pokemon are not compatible, the man outside of the Day Care will say "The two prefer to play with other POKéMON than each other." Any other message means that they will breed. Here is a list of all possible Day Care messages:

"The two seem to get along very well."Pokemon will breed quickly.
"The two seem to get along."Pokemon will breed.
"The two don't seem to like each other."Pokemon will breed slowly.
"The two don't seem to like each other."Pokemon won't breed.

After dropping off the two compatible Pokemon, you need to walk, run, or ride your bike. The game will decide if an egg is generated every 256 steps you make. The likelihood of the two Pokemon making an egg in that 256th step is based on the IVs of each Pokemon. This guide won't go into those details. Just know that as long as your Pokemon are compatible, they will eventually make an egg. The man in front of the Day Care will give you an egg if available. Make sure you have a spare slot in your party.