What are the four most important things for an attorney to remember when setting up a reciprocal referral arrangement with another attorney?

According to ABA Model Rule 7.2(b)(4):

1. The arrangement "must not be exclusive". For example, a lawyer must not promise to refer all criminal law clients to his one friend and to no one else. 

2. The client to be referred "must be told about the referral arrangement." Furthermore, if the arrangement creates a conflict of interest for either attorney, the lawyer must obtain written, informed consent. 

3. The referral arrangement must "not interfere with the lawyer's professional judgement as to making referrals."  

4. Reciprocal referral arrangements should "not be of an indefinite duration" and they should "be reviewed periodically" to ensure that they continue to comply with the ABA's rules and regulations.