Hint: Find/Capture/Enslave Ho-Oh
After you beat the Pokemon League, go to Viridian City and locate the old man near the Poke Mart. Talk to him when you have all the badges, and he will give you the Rainbow Wing. Go to Ecruteak City and enter the Tin Tower. The man blocking the stairs will see that you have the Rainbow Wing and let you through. Work through all the floors to the roof. There's a single Ho-oh (L40).
Hint: Get Baby Pokemon
To get a baby Pokemon, you need to go to the daycare center right below Goldenrod City. Give a male and female to each of the two people. Give the following Pokemon to get the listed baby Pokemon:
- 2 Pikachus: Pichu
- 2 Clefairys: Cleffa
- 2 Jigglypuffs: Igglypuff
- 2 Electabuzzes: Electkid
- Mr.Mime & Jynx: Smootchum
- 2 Magmars: Magby
Hint: Capture Lugia
To capture Lugia, you need to go to the Whirlpool Islands near Cianwood Island. But first you need HM06 and the Silver Wing by defeating Team Rocket in the city before BlackThorn, and also defeating Team Rocket in the Radio Tower. Then after you get those items,go to Whirlpool Islands. Use Whirlpool to get past the whirlpools, then work your way through the maze. A Lugia (Lv.40) should be at the end.
Hint: Get Celebi
To get Celebi, you have to catch Suicune, Entei, and Raikou, and then trade in Articuno, Zapdos, and Moltres. Then, go to Viridian City in Kanto. Outside of the Battle Station there should be a woman. Talk to her, and she'll give you a GS Ball. Go back to Ilex Forest, and get to the shrine. Put the ball in the shrine, and Celebi (level 5) will come out of it.