The key to being a good ranger is understanding the habitat of creatures. Once you know what you need to tame for your skill level, you simply need to find a region where you can find the creatures. There are many good areas to tame. Generally, places that are not saturated by other tamers and have a good respawn rate are ideal for raising taming. Tamer saturation will vary across shards. There is no one "best spot".
These regions contain almost everything necessary to reach grandmastery, since you can gm off of great harts, bulls, and dire wolves. Other creatures found here include: hinds, sheep, cows, bulls, goats, mountain goats, timber/grey wolves, cougars, panthers, brown/black/grizzly bears, great harts, eagles, giant spiders, and snakes. Be weary, though, as there are also plenty of monsters here.
Just south of the city gates of Trinsic is home to a fairly large spawn of creatures. This seems to be a bit more "tame" than the area around Yew and Wind. Creatures here include: hinds, sheep, cows, bulls, goats, timber/grey wolves, cougars, panthers, brown/grizzly bears, great harts, eagles, giant spiders, snakes, and bulls. There is still a fairly large monster spawn, which should be ample to help dispose of your tames, yet not too dangerous to tame.
A wide abundance of creatures can be found here with low monster spawn. However, the spawn radius is fairly small. You can find timber/grey wolves, brown/grizzly bears, great harts, eagles, snakes, bulls, horses, sheep, cows, and mountain goats.
This is the frozen island near Moonglow. This island is the only home (aside from the area outside of Ice dungeon on the T2A side) to these creatures: walrus, polar bears, snow leopards, and white wolves. These creatures spawn most heavily at the southern tip of the island. You will also find the occasional orc camp spawn. Dungeon Deceit is also here as well as a shrine. Across all shards, this is the most popular area to tame.
Along the eastern wall of Trinsic is a bridge leading to Barrier Isle. It is home to bulls, great harts, goats, cows, horses, and llamas. A nice quiet, out of the way location with an occasional aggressive spawn.
Just behind the healer's hut and outside of the western walls of Delucia, you can find bulls spawning in relative abundance. Cows, hinds, goats, sheep, mongbats, and horses can also be found here.
This area is far to the north of Delucia, slightly northeast of the City of the Dead and the Orc Fort. Creatures found here are primarily hind/great hart spawn camps and the occasional horse or llama. The only monsters found here are in the form of orc camps. Over time, all creatures that spawn in the form of camps will vanish.
The only creature that spawns here for taming is the snake. Other low-level undead (skeletons, wraiths) spawn in the area, as well as the occasional giant serpent and rare silver serpent.
There are several regions where giant toads spawn. Featured here are the 4 locations outside of the 5 spawns located near the entrance of fire dungeon. The one for hoppers bog has at least 4 toads that spawn there. Only 2 regions do not spawn silver serpents.
This is where I achieved gm taming. Most common creatures include: lava lizards, small and large hellcats. In the swampy areas, you can find snakes, alligators, giant toads. Be weary of efreets as well as the newly implemented lava snakes and serpents. This area has become extremely dangerous to tame at since the release of UO:R. The safest way for you to tame is from a boat on the east coast, at the expense of healing, since you will no longer be able to get out of sight to tame anymore.
You will find the same creatures inside as you do outside, only in smaller numbers. This includes lava lizards, small and large hellcats, and hellhounds. You will also find the dangerous efreet on the lower level.
Found on the Isle of Fire, Hythloth is most commonly visited for the daemons that spawn in the lower levels. Before the addition of T2A, Hythloth was the top place to hit gm taming with the native hell hounds. Hell hounds and imps spawn here to tame. Be weary, though, hell hounds spawn in packs and are usually found in small rooms. Opening doors can sometimes open a tide of hungry puppies.
One of the newer areas of Ilshenar. Dire wolves, ridgebacks, great harts, and black bears can be found here in abundance. It's not too terribly far from a shrine. This also happens to be "savage central", so be careful when in the area.