Unfortunately, catching it early is not always easy.
There are some symptoms that you can watch for:
1) Wobbliness, walking around acting a bit drunk
2) Drinking a lot of water
3) Vomiting
4) Refusing to eat
5) Not wanting to get up
The best treatment is PREVENTION.
At home, make sure that your radiator does not leak and that you store any antifreeze containers out of the reach of your pets.
If you do have a radiator leak, soak up the antifreeze liquid into paper towels and throw the material away or throw cat litter or dirt over the leak, then sweep up the material and dispose of it into a sealed trash can.