Lots of good advice here. As for repetoire - ignore what the finger flingers are doing and what impresses other magicians and keep alert for things that entertain lay audiences. You're being hired to provide entertainment. Sponge Balls/Sponge Rabbits, Color Changing Knives, Copper/Silver are old to magicians but almost always new to lay people. (I worked Polaroid Money for 20 years before I heard a woman say that her husband had a "trick wallet" like mine. Once in 20 years isn't bad.)
You have to know your material cold and be able to do it in your sleep as you'll be performing in dynamic and fluid situations, constantly adjusting for what is happening around you. You cannot think about your material as you perform. You have to focus on adjusting the presentation to the situation all the while being aware of drunks or smart asses who want to show how clever they are, grabby kids, etc. Most people are polite, but you must be in control at all times and prepared for what can happen.
When I worked for the Trader Vic Organization many years ago, almost nothing I presented took longer than 90 seconds, but nothing seemed hurried. The effects were simple, so the specators understood what had happened. Nothing complicated or anything that required counting cards or making piles...
Everything came out of my pockets. I worked standing at the table, not sitting like Allerton did.
My presentation was modular. If I detected the slightest flagging of interest, I'd stop, thank them for their attention, and walk away. I learned never to over-stay my welcome or to push myself onto people who were merely being polite.
Learn how to approach people without being intrusive. Two men discussing business will not be interested in watching you do a card trick.
On party walk round - I work out of my pockets and, occasionally, with a simple, small table, as there are things I like to do that require a table. Everything is "correographed" that that whatever I'm using goes back to the same place. I've spent a lot of time working out the logistics of what I'm doing and where it goes on me. You must be organized, but not with too much on your person so that pockets bulge and you cannot access things easily. I usually have a 20-minute repetoire on me, but that is usually overkill.
When I am working a [censored] party where there are tables, I use them, not my table, watching out for spilled drinks and dropped food.
If you are working a large party, develop two or three short routines of three tricks that can be done in their hands for small groups of three or four in a short time. This way you can cover a large group, do a little at each small group and move on. You're being hired to "work the crowd," not stand in one place and entertain one group of people for 15 minutes. I've worked a number of large parties where I did the same three or four tricks for tiny groups for two hours.
Not long ago I worked a house party where the caterer insisted that I work the tables instead of doing a single stand-up act. So, I did ten minutes at each of the six tables of 11 guests, varying my presentation from table to table.
While it was a party for adults, the hosts' children were present. I used them twice, which delighted mommy and daddy. By the way, no sucker tricks for the kids. They were treated with respect like the adults, which was recognized by the host with a nice tip for "being nice to my kids."
Something not touched by others: clothing and manners. Being appropriate and sophisticated is important, especially when working country clubs and corporate events. For most of my work I wear either an Oxxford tuxedo or an Oxxford cashmere blazer, a custom shirt and a Brioni tie. Naturally, the hair is groomed and my clothes, hands, and breath are clean. I look like the people who hire me. They think you're "one of them" and you gain respect and attention right away.
There are several good books on manners. Read at least one if you have any questions about how to behave.
You would think this need not be mentioned, but I've actually worked walk around with other magicians who look like they've slept in their cars before the show....rumpled suit, black tee shirt instead of shirt and tie, etc. Amazing that they work at all.
And I wear a name tag that identifies me by name and profession, so when I join a group, they instantly identify me as the entertainment. While I've worked a few parties where the host did not want me identified as a professional entertainer, but their "friend who did magic," the normal approach, with a name tag, makes things much easier.