You need to receive a Clear Wing from Spinda. With it, you can visit Entei, Raikou, Suicune and Ho-Oh. You can only recruit Entei on the second visit or more. To improve recruitment rate, you need a high rank, high level Pokemon and a Friend Bow. This method works with Suicune and Raikou.
Entei level is 45
only if yhe legend on your team is small like entei can recruit suicune i think
wherever you want him to be
Entei
You can recruit Aerodactyl in Sky Tower :D
I believe if you look at red rescue team it is the same.
the 3 dogs are all a size 1
Wish Cave 99F
recruit the legendary birds
You can't recruit Pokemon in Tiny woods
Actually I don't think you can recruit any Pokemon really easy
15% You can recruit suicune raikou and entei with a better rate if u obtain a friend bow through wonder mail