What a sweeping comment to make. Although I see why you'd say that (probably have read a few things saying diet plays little part, skin irritation causes acne etc etc) the amount of effort and research I've put into cleaning up my skin including reading hundreds of articles on it, reading countless forum posts reading what people suggest and seeing numerous dermatologists (in fact my aunt actually is one), and most people's acne is aggravated by many of those points. Yes, a lot isn't 'proven' (although the notion that diet plays no part in skin care is one that's now being laughed at by dermatologists), but to have someone come along and say 'According to the literature' when they have no idea of how much knowledge the previous person providing the advice actually has on the subject is not only unfair on the OP, but also just out right arrogant.
I'll break down the reasoning of the post I made the other day as at the time I was in a rush and perhaps didn't go into it clearly enough. Basically different people have different 'triggers' which result in acne. High GI foods and dairy are accepted to be one of the more common triggers. For some people cutting both out would be beneficial, for others changing that aspect of your diet will make very little difference (although the derm I saw at sk:n swore that nearly everyone she told to cut high GIs out saw a major improvement). This is one of the things I did which made the most difference to my skin. Dairy doesn't really make a difference for me, but GIs definitely do.
Drinking 4 litres of water per day along with taking vit D, omega 3 (stay low on omega 6), vitamin C and zinc (as soon as I started taking 50mg per day of zinc along with 1000mg of EPA/DHA (omega 3), my skin pretty much became flawless. Worked with my brother and my cousin.
The steaming advice will work if done once every 4 days (or once a week for people with oily skin), the trick is not to overdo it as that'll lead to your skin producing excess oils which will clog pores and lead to more acne.
The idea that somebody could say having dirty pillows doesn't effect acne is laughable.
Realistically OP some of those points will most likely work for you. After 3 years of bad acne and hundreds spent on products, my skin finally became good after I started following those points above. Right now I have no spots whatsoever and my skin care routine consists of using a cleanser, a salicylic acid treatment lotion (although haven't used that in weeks as I haven't had any spots), a 'maintenence syrum' with malic and mandelic acid to keep pores clear (again, don't really use unless I get an oily face which hasn't happened since I started on the vitamins), and then I exfoliate once or twice a week.
My brother's 17 and had awful acne. He'd tried oxytetracycline, differin, duac etc, and was considering accutane. Then he cut out GI foods, cut his milk intake in half, change his bedsheets weekly and started on the vitamin routine, and with the same skin care products that hadn't been working for months, his acne cleared up within a month. He has 1 spot on his entire face.
So listen to timeofflight if you want to. She's probably done a fair bit of reading - maybe even a few scientific studies - but I can guarantee I've got far more experience in this department.