http://www.wowprovider.com/?talent=1121 ... 322215105n...is pretty much the basic feral spec for anything that isn't pure tank or DPS, which a feral druid should never attempt to be. If you want to be more tank, you take 5/5 Thick Hide instead of Feral Aggression. If you don't want to tank at all, you take the points from Primal Fury and finish out Natural Shapeshifter.
You definitely don't want to waste points on Thick Hide in a leveling build, that would be beyond retarded even if you intend to tank a lot of instances. It's a weak talent overall as it doesn't stack multiplicatively with the bear form bonus, so it only gives a few hundred armor. It's only really worthwhile if you're tanking raid content.
You want to take Furor fairly early, probably in your 20s, because you have to shift out and heal yourself pretty often while soloing. If you have to regenerate a full bar of energy each time you shift back into cat form, it slows your grind down a lot. Furor is also pretty much necessary for tanking as you need to be able to start the fight with enough rage to use an ability, otherwise you're always behind on aggro.
Assuming you want your leveling spec to both grind solo and tank instances, here's a sensible progression model:
20
http://www.wowprovider.com/?talent=11215875_11_8q51p5n30
http://www.wowprovider.com/?talent=1121 ... q55d213j5n40
http://www.wowprovider.com/?talent=1121 ... 032221c05n50
http://www.wowprovider.com/?talent=1121 ... 22215105m0You take the balance stuff last because it's a gigantic investment for just +10% damage, as well as the Shred talent since that's not very useful while leveling.