Google looks down upon paid links for enhancing page rank. If a website sells links, what action/s does Google recommend to avoid being penalized?

Q) Google looks down upon paid links for enhancing page rank. If a website sells links, what action/s does Google recommend to avoid being penalized?

Answers:
• The text of the paid links should state the words "paid text link" for Google to identify it as a paid link
• Only Paid text links to non profit websites should be accepted
• Paid links should be disclosed through the "rel=nofollow" attribute in the hyperlink
• Paid links should be disclosed through the "index=nofollow" attribute in the hyperlink