First, there is no tricking your wife into swinging.
Just like when your eyes light up at the sight of a hot woman, your wife is going to notice your attempts to get her to try swinging.
You know your wife best or at least you should- LOL
The fact that you are asking this question means you do not think your wife would be interested in swinging. You could be wrong.
You have to start talking about sex with her.
You need to find out what arouses your wife.
The approach is everything.
1. The point is to start talking about your sex lives.
The discussion could start like this.
The most memorable sexual encounter with you was....
First, you finish the sentence and then ask her to finish it.
The reason you go first is to break the ice. She will love that you put some thought and effort into it.
Listen to her as she describes the most memorable sexual encounter. She is going to give you clues into what she liked about that sexual encounter. You can start there.
Once the sexual lines of communication are open, talk about positions she wants to try, what she considers foreplay, her favorite foreplay moves, her arousal points (lips, ears, back of neck). Now share some of your favorite foreplay moves, sexual positions and arousal hot points.
Once you get comfortable talking about your sex lives together, other topics like fantasies get easier.
2. Almost everyone has fantasies.
Fantasizing about an actor opens the doorway to discussing sexual fantasies. Of course, it is not likely your wife will actually have sex with that movie star. Just the fact that she would consider a sexual fantasy with a movie star is a step in the right direction.
You could ask her if she has ever considered sex with another man or woman. The cop who puller her over, the clerk at the store, that hot guy at the gym.
She may say no way would I have sex with another man. If she says no, then you need to figure out if something is holding her back. Is she religious?
Religion can hold back a woman from living out her sexual fantasies by causing lots of guilt. If your wife is 30 or older, then it could be the social and ethical hang ups that are causing the knee jerk "no". These women were taught not to sleep around.
She may say yes. Then ask her to talk about it. You might even get laid because she will get sexually aroused just thinking about it and you are right there to satisfy.
She may refuse to answer the question. When she refuses, then you will need to be patient. Time will tell as the sexual communication lines open up. She is just not comfortable to answer the question.
The suggestion of swinging can really catch your wife off guard. It causes all kinds of thoughts and feelings. Some good and some bad.
You need to be reassuring and sensitive to her feelings.
Examples of good feelings:
1. Maybe she secretly fantasized about swinging.
2. Maybe she would like to try bisexuality
Things to watch for are feelings of doubt about your relationship.
You need to think of your wife first when talking about swinging.
Bottom line: Keep the lines of communication open between you and your wife about sex and anything else too.