Here's some general advice for single guys looking to hook up with couples. Just to be clear, we play with other couples, single women, single men, and groups. We meet people online, at clubs, and other events. We've been in the LS for three years and play a few times a week. We frequently travel to play and have met with people from all walks of life.

1. Work on your intro, whether it be online or in person. Don't just just say "Hi". Lead off with a greeting, compliment the wife, and share something about yourself to prove you are a human being.
2. When online, leading with a dick pic is often a bad idea. Read the profile to see if the couple wants pics up front. If they don't explicitly state they want a dick pic, then wait for them to ask. However, leading with a face or full body (clothed) pic is a good idea.
3. Don't brag about how hard you'll fuck the wife unless you get an indication that the couple is looking for a cuck situation. Most swingers have phenomenal sex lives. Thinking you are stepping in to offer a "better" experience is foolish.
4. Be engaging to both halves of the couple. Compliment the wife, and be respectful and friendly to the husband.
5. Shower and practice good overall hygiene. If this needs further explanation, this lifestyle isn't for you.
6. Dress well. You don't need a $1000 suit but you should put your best foot forward with your clothing choices.
7. Stay away from couples that want to see a bank statement.
8. Take rejection with grace. Couples talk about their bad experiences, but even if you aren't their cup of tea they might talk you up to others if they see you at a party.
9. Know your own limitations. If you have a known issue with getting or staying hard, or you're brand new and don't know, then plan accordingly. Take viagra or cialis, use trimix, or pregame with some pot. Stay away from alcohol. Whiskey dick is real.
10. Don't overstay your welcome. Read the room and understand when the party is over. This will increase your chances of being invited back.
11. If you aren't used to condoms then practice with them beforehand.

This is not a comprehensive list. It's just some general advice that any single guy, regardless of financial status or station in life can follow to increase their chances for success.

---Additional tips from commenters---

1. Be prepared to be rejected. A lot. There is a history of single men acting like animals/losers/creeps/etc. that you have to overcome. It may not be you; it may be all of those other guys before you.

2. When online if they say no single men - respect that boundary. You're just wasting their time and yours.