Your daughter is adorable. <img src=""> Some people disagree about the precise order of nebulized meds, but always always do albuterol first, since it opens up the airways. Then the rest of the medicines can be breathed in easier.
Also about sterilizing, it's best to sterilize them after every single use. BUT it's rare that anyone really has the time to do that, so if you do it once a day that is probably sufficent. I think most people just toss them in boiling water then let it cool. Personally I found these online:<a target=_blank class=ftalternatingbarlinklarge href="http://www.amazon.com/Medela-Quick-Clean-Micro-Steam-Bags/dp/B000096QQ5/ref=pd_bbs_sr_6?ie=UTF8&s=baby-products&qid=1210399363&sr=8-6">Medela Steam Bags</a>and they are amazing. Just toss the nebs in the bag, 2oz of water, and microwave for a few minutes.
Bah, edit: I just realized you're talking about an aerochamber which is slightly different. I honestly don't know how often those should get cleaned, since I never use them.
I'm sure lightNlife can answer that question.