What is a polite way of talking about a recently-deceased person?

Solution 1:

The phrase you are looking for is "may he rest in peace". "Robin Williams, may he rest in peace, was..."

The phrase "God put him in Heaven" would sound charmingly exotic. The person you are speaking to would likely have never heard it before, and your sentiment would sound all the more touching and sincere for its unfamiliarity.

"God forgive him" implies you think he did something terribly, terribly wrong. The clear implication (to a native English speaker) is "may God forgive him because I won't."

Solution 2:

The previous answers are well and good, but you can also be respectful when talking about a recently-deceased person by referring to them simply as:

"The late Mr. Smith..."

This is a formal (and thus, respectful) indication that Mr. Smith has recently passed away, and also avoids any reference to religion, in case others might take offense or discomfort.

Solution 3:

If you want to retain the use of the word "God" you could use the following:

"Mr. Smith, God rest his soul, ..."