Live performances are such an awesome part of noise. If you don't do them, or at least attend them regularly you are really missing out.
I think I started performing noise live just like Mattias G. And I feel the same way as he did, regarding becoming more comfortable with your sounds and realizing that "less is more" sometimes, but also having to capture the attention of the audience as well.
One of the many things I love about live noise performances is you never know what you're going to get. Like Mikko said, there are so many different ways to create sound and do your set, but I have seen more industrial related bands use junk metal and strange objects successfully before. I think using a mixture of sampling, electronics, and physical "playing" is the way to go. But I tend to have a number of 3-8 tracks which I can perform at one time and when I find myself playing 3 shows in a month I'll do different variations of those tracks. Some of them only require simply a sampler, others are more complex using live cinderblocks, glass, metal, and homemade instruments. If there's a smaller show that I know won't be well attended and I'm playing it just to be exposed to a different crowd, or as a favor to a friend I might do a simpler set using only synth and mixer. If I'm doing a big show with other acts that I really respect I'll do a newer track that requires a lot more energy. I also sometimes tailor my sets to mix in a little more with the style of the other acts on the show. I was just telling my gf the other night that I really love how I am actually influenced by the acts that I play with now and it's interesting how they can affect my sound.
Sets can also be determined by logistics. When I did my West Coast tour, obviously I couldn't bring materials like glass, stone, metal, machine parts, along with me so I did what I could with my pedals, a small piece of sheet metal, and samplers/synths. I still got a lot of responses to the sets, I think because it had enough of an auditory dynamic.
I think when you have some physical element in your set it's automatically more "accessible" but I personally don't care if it's just a person at a laptop - if it sounds great I am usually really engaged in the set.
