Savannahs are very common biomes that can rarely be really small but very often pretty large. Because of their size it's not hard to find some sooner or later, still you might have to cross larger bodies of water (Oceans) to discover them for the first time; depending on where you have started.
These warm to hot biomes are usually flat with large, but only very low "hills". They can be recognized easily by their yellow-ochre Savannah Grass on the ground and occasional Parchwood-trees with golden-brown flat cloudlike tops.
In hot areas within Savannahs inflammable materials can easily be set on fire, for example by placing a torch on a tree under a block of wood or leaves. This fire can then spread and Parchwood-tress can burn down together with their neighbour Parchwood-trees if they are too close by.
Savannahs are a bit dangerous because of aggressive BossHogs that will attack if you get too close to them. Shrewdshrews are normally peaceful, but if you try to tame them or hurt them, they will defend themselves fiercly, even by spitting fire. This can set inflammable materials like dry vegetation on fire, and even whole Parchwood-trees might burn to nothingness if the area is hot enough.
While Shrubs, Savannah Tallgrass (can have Wheat Seeds in it when harvested) and patches of Wildflowers (not to be mixed up with Wildwood Flowers growing on Wildwood-trees in Jungles) can usually be found on Savannah Grass, these plants do not seem to grow on artificial biomes made from these blocks. However it is possible that Wildflowers might very slowly regrow in natural Savannah-biomes after an area has been freed of these flowers. Savannah Tallgrass and Shrubs can be used as Fuel for the Forge.
Most often there will be a few layers Rocky Dirt below Savannah Grass in natural biomes instead of the usual Dirt, and with no Brown Mushrooms inside. Just below the Rocky Dirt the Fossil layer will start with a lot of Stone in its topmost layers.
Usually a number of tunnel-like caves can be found in any Savannah. Here Night Pigsies and Night Rocksters can spawn and come out of caves, also perhaps a few Mirus; all of which will burn away in sunlight, but can be dangerous at night.
Parchwood-trees do not grow any flowers, Moss nor Vines, however occasionally you can find Queen Bees and/or Beeswax amongst or on top of their leaves. However often Queen Bees might not grow into Beeswax in Savannahs but stay fallow when the area is too hot.
In some Savannahs, a few very small bushlike Ashenwood-trees with a few patches of Moss and/or small Cragwood-trees with a few Vines can be discovered, perhaps next to one of the small lakes. These small trees only rarely bear any flowers.
Rarely you might be able to discover oases within Savannahs with Shorewood-trees close to the Water and perhaps even a ring of Sand around the lake with a few Seashells on it. On Shorewood green-blue Chizzards will often spawn, and at night Night Chizzards. Also Rocksters and/or Pebbles might be seen in such areas, which means Night Rocksters can easily spawn at night there too.
Jungle-biomes are often, but not always, close to Savannah biomes. If you have troubles with finding Jungles on your world, then you might want to try circling larger Savannahs.
Wood Treasure Chests can occasionally show up during (ingame-)night-times in dark places in range of view of player-characters in Savannahs. These valuable findings can also spawn on tree-tops and/or at cave-entrances.