I really enjoy doing shows for private parties - small groups of 10 to 20 people at their home after dinner. It's quite a magical experience all round.
I did one last night and here are a few tips and observations:
1 - Try not to carry too many decks on you at one time to avoid confusion. About 12 is the limit. I accidentally gave someone a Deckstress deck to shuffle and no, they don't survive the shuffle...
2 - Performing some effects on the floor with people sitting in a horseshoe shape around you is an ideal setting. I prefer it to a table because it gives everyone a sense of direct contact with the performer. The table almost acts as a "fourth wall barrier" between the performer and the participants.
3 - I call them participants because, in such small groups, it's possible to involve everyone personally. Whether they are holding a card or a rubberband, they take part, and they should be acknowledged as they key ingredient in the trick's success, not treated as props.
4 - In these settings you can afford to do longer, story tricks. I got to do my version of Heirloom, 'Poker Alice', from the 'Poker In The Face' show. In normal close up there are way too many distractions. But at a private party everyone listens to every word and was almost gasping in disbelief before I showed the photo of Alice holding their chosen card.
5 - A tangled Gypsy Thread is not nearly as impressive as one that unfurls smoothly.
6 - Utilise the environment. Last night I had them put a prediction in the freezer for safe keeping. At other parties I've asked everyone to follow me into the kitchen where we got an orange and a knife to cut it open with to find a bill inside. Think of how 'The Mentalist' plays it on TV. He never seems to carry props with him, he uses "found objects" and in a private home situation that can be incredibly powerful.
7 - Never treat it as a "gig". You've simply turned up to pick up a cheque, and while you're waiting for them to write it out, you might as well do a few tricks to keep everyone amused.
8 - Do you dress more casually for these events, or wear your standard "magician" costume? Still undecided. I wear my blue jacket pretty much everywhere. It's not quite as formal as a tuxedo, but it designates me as 'The Magician', a special visitor. Perhaps your costume might make you look ridiculously overdressed at an informal party? (Maybe mine does too?) Something to ponder.
9 - Mentalism effects play more effectively in a private party environment but, unless that is your character, don't do too many or the tone of the party will shift from "fun and amazing" to "sombre" as party people start to ponder the deeper questions of life and the hereafter.
10 - Don't stay on after the show for drinks and nibbles. They will always ask you to stay. I'm told it's "hospitality". However by doing so you risk destroying the air of mystery and magic you've just spent the last 30 to 60 minutes creating. Arrive set to perform, go straight into your show. Do your big finale and them leave. The front door is your wing, your stage entrance and exit. If they book you for a 30 minute show, do your 30 (maybe a little longer if you feel generous) but then take your applause and leave. Leave them to discuss the wonders you created amongst themselves, and not debate them with you. Again, look at 'The Mentalist'. He leaves people intrigued by popping in, doing or saying something odd, then leaving. It's the way of the magician.