There are several different styles of swinging which you may see in the swinging community. Some people may prefer not to be around when their partner is having sex with someone else ("closed swinging"), while others may insist on it ("open swinging"). The term "soft swinging" refers to trading partners just for the purposes of heavy petting and then switching back to one's primary partner for any actual sex. It might be valuable for you to think about whether there are any potential situations that you feel you would be more or less comfortable in, and discuss these with your partner.
Although not all couples find it necessary to do this, some couples feel more comfortable having social "codes" that only the two of them know. Examples might be discreet phrases or gestures which mean a) one of you is attracted to the people or person he or she is talking to and wants to know if you are interested in swinging with them, b) a reply to the above, either affirmatively or negatively, and c) one of you is not having a good time and wants to get away from things for a while.
At off-premises events such as dances, it's common for people to dress up or else wear fairly sexy clothing. Dress at on-premises events tends to be more casual, since nudity is a common outcome of the evening for many. At on-premises clubs it's a good idea to bring something like a robe so you don't have to put all your clothes back on after sex, and to avoid wearing lots of jewelry that might get lost. If there's a dress theme for a particular event, go with the theme.
By the way, it is not necessary to actually have sex with other people to have a good time in the swinging community. Off-premises activities such as dances can provide a wonderful opportunity to flirt and be flirted with in a non-threatening yet sexually-charged atmosphere, which can be fun in and of itself. On-premises activities can provide an opportunity to appreciate the sights and sounds of sex as an enhancement to sex with your primary partner, whether you two decide to have sex at the party or after the party.