1) Always obtain permission from your seller client on how they want to proceed.  There is a very low probability that someone will back out when notified of being in a multiple offer but there is always the risk and the client needs to understand this.

2) When dealing with agents verbally (or otherwise) make no promises that your client will accept an offer.  If a change needs to be made and the buyer's agent lets you know verbally that the buyer will do it, best to tell the buyer's agent to get the change signed and back to you for signatures and let them know that you make no promises as up until it is signed another offer could come in that is better for the seller client.

3) Even when you have put all parties on notice there may still be the opportunity to better your seller client's position.  When offers are close you can make that last phone call to the agents asking again if there anything additional they would like to do since offers are close.  This would be pending the seller client's permission and re-explaining the risks of losing one or more of the offers.

4) Have your seller be last to sign.  This a great practice period.  

5) Gracefully, keep pressure on the agent(s) who seem to be bringing the most to the table.

6) Understand that some agents need help in these situations and by helping them in a sympathetic manner things can happen that will surprise you.

7) The whole idea is to have something that is suitable for the seller client to sign and have acceptance (not waiting for signatures or initials on counter-offers coming back from buyer after seller has signed/initialed).

8) When you are dealing with an agent who delivers incomplete documentation, missing signatures and/or initials or a combination of the foregoing move slowly and express your desire for having complete documentation, signatures and initials so your seller can take it seriously and hopefully sign it.  This actually applies for any offer but is very important when dealing with more than one.

9) We want to give all agents the best chance at obtaining the property for their client.  The client's desire and willingness to provide the most favorable terms is very important.  How the other agent presents the offer and handles things is important.  How we interpret the information and tactfully navigate the process is equally important.

10) It is no fun telling agents their client did not get the property but in the end as long as we handle things professionally it usually turns out that the ideal buyer prevailed.