Firstly let’s cover the basics, which you are probably already familiar with.
When performing be open and engaging. Plant your feet solidly on the floor, stand up straight, shoulders back with your arms in an open position. This applies when performing close-up magic, not just on stage!
This will give you an air of confidence, and this will help when having to introduce to a group of people or when coming onto stage. It also opens your airways so you are able to ‘project’ when you talk so you are easily heard by everyone around a table, even if there is background noise.
Don’t hunch over, and make sure what you are doing, and the props that you are holding, can be easily seen.
In fact, these ‘basics’ are covered in the book “Magic and Showmanship” by Henning Nelms (a relatively cheap book and definitely a book you should read) when discussing the how to present yourself on stage. This book also goes into more details on stagecraft and the crossover with how your body language is perceived by the audience is clear – even if that wasn’t the intention of the author when the book was written.
Be conscious of your actions and body language when performing, not just on stage but also when performing close-up and around tables.
Lean forward to engage with people, but not so close to trespass into their personal space – you don’t want to be intimidating the spectators. Once people are drawn in you can lean back a little, and this will subtly draw them into the void and focus their attention on you.
When presenting you will want to ‘change gear’. What I mean is changing the style, presentation and pacing of the tricks. This change keeps attention of the audience – go back and see the Lessons about selecting tricks in the Children’s Magic Section as principles are same regardless of the age of the audience.
Add emphasis to this change of pacing by changing your body language. For example, you start with open body language to gain control of the situation; but now you wish to shift the attention from you to the prop in your hand, and build tension and suspense prior to the magical moment. Now reduce the volume of your voice, slow the speed of your speech and start leaning forward. Your eyes go from looking at the spectators around you to focusing on the object, and their eyes will follow; along with their focus of attention.
As magicians we tend to focus on misdirection, getting the spectators to look away from your hands (or prop) so that we can perform the secret move. In reality actually want to give them direction, and make them look where we want them to. It is easier to get someone to look away from one thing if they are given something else to look at.
More subtle effects can be achieve by shifting your balance and what leg you are leading with. You may be standing with you left leg forward of the other and that one is taking the majority of your weight, and you simply shift you position by swapping legs. This is should be done not randomly, but between smaller changes; for example between phases of an ambitious card routine. It’s not something that will consciously noticed by the audience, but will aid to slightly break up the flow. (Imagine that the individual tricks are the scenes in a film, but the change of position is like changing the camera angle within the scene).
Although I recommend keeping as ‘hands off’ as possible when performing, with close-up magic there will be occasions when you will need to make physical contact with spectators. Do this once you have rapport, and select someone who is already having fun and getting into the magic.
Avoid invading someone’s personal space, and be aware that even just the simple act of placing objects in someone’s hand and holding their hand shut (for example loading sponge balls into their hand and positioning it into a closed fist position) may make some feel uncomfortable. Also be aware that though the person involved may be fine with it, it’s possible that their partner may be feeling a little over protective.
On the subject of touching, it is sometimes beneficial to very lightly and briefly tap a spectator on the upper arm once you have established rapport with them. Without getting to psychology, it helps confirm and strengthen rapport, but in a non-overt way; and if the rapport is genuine it will likely go unnoticed by the spectator on a conscious level.
Be aware of the body language of the group, and individuals within the group. You’ll notice that spectators will visibly relax as they get to know you, which will not only make them more willing to join in with you, but will also make them enjoy the performance more.
Observing body language is also beneficial when approaching a group of people, and working out who will be best to approach to initiate dialogue with. You can also spot if there is a dominant person in the group, and now know to take them into account.