Breeding Guide
South of Goldenrod, there is a house where an old man and an old lady takes care of Pokemon. Give a male Pokemon to the old man, and a female Pokemon to the old lady, and walk through the south door to check on them. If a message that says "Shows interest" or something like that, then the two Pokemon could produce an egg. Just keep walking around, then return to the house. If the old man is outside, congratulations, you have an egg. The egg will be a Pokemon matching whatever the female Pokemon was, and it MAY inherit some moves from the male Pokemon in the breed. All Breed-only moves are obtained through one or a series of breeds until the baby Pokemon learns it upon birth. If you just want a baby Pokemon, just use Ditto since it could breed with just about any Pokemon.
Usually, an egg takes a few thousand steps to hatch. Some of the longest to hatch are Snorlax and Aerodactyl. The egg is a great way to get another of a special Pokemon like the starters. Some Pokemon are one-gender only, and some Pokemon without a gender could only get an egg by breeding with Ditto.
FEMALE ONLY:
Nidoran Female
Nidorina
Nidoqueen
Smoochum
Jynx
Kangaskhan
Chansey
Blissey
MALE ONLY:
Tyrogue
Hitmonchan
Hitmonlee
Hitmontop
Nidoran Male
Nidorino
Nidoking
Tauros
NO GENDER AND BREEDABLE WITH DITTO:
Magnemite
Magneton
Voltorb
Electrode
Staryu
Starmie
NOT BREEDABLE:
Unown
Igglybuff
Pichu
Togepi
Cleffa
Tyrogue
Smoochum
Elekid
Magby
Articuno
Zapdos
Moltres
Raikou
Entei
Suicune
Lugia
Ho-Oh
Mewtwo
Mew