Having sex with multiple partners can mean one of two things:
Having sex with more than one individual at a time
Having sex with multiple individuals consecutively
Finding additional partners
It is not difficult to add individuals to your sexual experiences and relationships. Today multitudes of dating sites bring together individuals solely for this purpose. Be as clear as possible in your ad to ensure only the best candidates apply. If you are worried about online advertising because of your public profile, it may be easier to glean through your inner circle.
If you wish to make it an adventure, try visiting a local bar with your partner.
Have ground rules
Ground rules are important in any scenario. They are especially important if introducing a new partner into an existing relationship. Ground rules should spell out where activities will occur, how often, and if any activities are off the table with the new partner. Check with new partners if they have any hang ups or issues before engaging in any activities. If you want your partner(s) to trust you, stick to the rules.
Finish what you started
New partners may be disappointing in the bedroom. It is hard to effectively "interview" a person in this way, unless you have had sex with them in the past. The likelihood of your new partner inviting an old one into your bed is low. New partners may have disappointing performance, body measurements or other unexpected blemishes. Continue on if the flaw is workable. No one wants to be told "never mind" once they have their clothes off.
Respect each other
In multiple partner situations, individuals may feel left out or jealous. This often happens in groups of odd numbers, and with couples expanding the boundaries of their relationship. Often these issues do not come out until after the activities occur. Work out any jealousy or insecure feelings that a partner or partners feel before engaging again.
If you invite others into your relationship, or have a poly amorous relationship, respect the privacy of all those involved. While a partner may be interested in sharing sexual experiences, this does not mean they wish everyone to know. Make sure your ground rules include the privacy requirements of all participants.
Sex with multiple partners is a way of expanding your sexual experiences and can bring new life to a relationship.