THANK YOU SO MUCH FOR ASKING!!!!!!!!!!!!!!!
Since this isn't your first powwow you may have noticed that Indians seem to be very quiet about new comers that make faux pas. It's true in a sense that many of us are laughing at them on the inside. Many people just think that because they have native blood or are interested that they can just come in and have it doing whatever they please.
Here are a few tips but I've listed the URL to a very good site on powwow etiquette. It's a Southern site, but that doesn't matter too much since many powwows in California follow Southern way and the etiquette is nearly the same where ever you go.
You asked about a shawl so I'm assuming you are female.
1. If you have a shawl please bring one. It is disrespectful for a woman to dance uncovered.
2. Since you are not fully dressed in regalia, you'll only be dancing during INTERTRIBAL SONGS, or public invited songs like the ROUND DANCE or TWO STEP.
3. About your clothes, this is my personal thing, so take it if you will. I personally do not wear shorts in the arena. Even though I'd have a shawl, I just think it's in poor taste. Now if my shorts are longer, like walking shorts, then okay, but for me, I don't like my legs to show. Many women including Indian women wear shorts, just not too short. But most women I see wear a longer short or cool pants.
Now that's all I have, you'll probably find more at this site:
If you have any other questions, I'm sure the other arena folks around here can help you. The main thing is to pay attention to what the MC says, he will guide and explain everything to you.
Hope you can make it!