I am in a similar situation, and learned some things recently, so here's my take on your questions:
Originally Posted by chouette
1) Does anyone have suggestions for constructive ways to communicate with potential new lovers about being in a poly relationship?
2) When is the right time to tell the new person about being poly? (Immediately? Before the first date? Before the first kiss? Before sex? Wait until they ask?). What’s the etiquette?
Considering you are married (not just in a very casual relationship), I recommend the etiquette be you new partner knows right from the beginning. She already knows about your wife, non?
When you decide to "make your move", "pop the question", open the discussion about dating, pick an environment where you can have a comfortable conversation. Either bring up your poly status BEFORE you ask, or have a plan to work it in in the first FEW SENTENCES after you ask. (I didn't think the conversation through and my friend thought I was asking to cheat...
Luckily I was able to raise the question again a few days later and clear it up.). This can be a bit awkward, but if it's someone who is interested in you she will probably be forgiving if you are not 100% "smooth"
Use language that she will understand. Many people may not understand "poly", so it can be things like "open", or "my wife has another lover and I'm also allowed..." "have you seen Les chansons d'amour?" Then, be prepared for questions and discussion: How does it work? How does wife feel about it? etc. She may need a bit of time to digest, so let her have it. (This actually worked REALLY well for me the second time I brought it up)
Okay, that's my answer to your questions, but I have one more suggestion based on my experience:
Do you have this fully worked out with your wife? Don't expect that it's just okay for you to pick up someone new. Make sure you have discussed the right protocols with your wife, and that she is ready and comfortable for you to bring someone in. It may be "yes, you can date anyone you are comfortable with" or you may need to clearly state you are planning to ask out the new person BEFORE you make your move, and work out the details with her.