I was just reading on Wikipedia (I know, I know :) that of about 200 nominations each year, around 20-24 are selected...and only one posthumous award each year.

Among other things the nominee must have"
- Worked 5 years in the award category being considered.
- Have a history of "Charitable Contributions."
- Donate $50,000 for the installation and maintenance of the star

One other thing for deceased members (in case anyone has $50K to throw away): "A relative of deceased recipients must attend posthumous presentations."