In Georgia how do I disinherit a grandchild from my estate?

All you need to do to disinherit a grandchild or other potential heir in Georgia is have a properly-drafted Will prepared and then ensure that your assets are owned and beneficiary designations set up in a manner which is consistent with your desired plan. It may also be helpful, although not necessarily required, to use a fully-funded revocable living trust rather than just a Will. An experienced estate planning attorney can help you figure out how best to proceed.