So, just browsing around online to see what I could find about house guest etiquette, I found the following tips to be the most common:
(Before I list them all here, let me just say that in our house there are some people who visit who we don't even consider guests- more like "non-guests"-- they've earned "mi casa es su casa" and they're the ones who don't need to knock- you know parents, siblings, best-friend neighbors, people who you're so close with that it would seem crazy to do some of these formalities with --- hee hee oh they get the royal treatment... we even let them help load the dishwasher ;) ;)) Ok, here we go:
1) Bring a hostess gift--- Especially if you haven't seen your friend for a while and/ or it's a special occasion or you're a first-time visitor... (but I must say that as a host, this is something I would never expect either, only that it's a nice surprise when it does happen.)
2) Help Out-- for example, ask to help with food prep, dishes, etc.
3) If you have kids, keep them under control-- I'd say this really goes for leaving the house at all (not just being a guest) but I thought I'd include it here anyway. Also know that people who aren't around kids a lot or don't have kids are sometimes more anxious about kids in the house than another parent with their own crazy kids. (Many exceptions to this of course, but I have realized how much more relaxed I am myself now when other kids are tearing through my house, compared to when I didn't have a kid... I guess it's like pain tolerance?? ;) ... Make sure to wake up with your children-- unless you're with grandparents, in which they usually relish having the kids when you're sleeping. (we hope!!) (image below from an abc show- not mine, I swear!!)
4) Keep your space tidy-- One of the articles I read mentioned that if you're in a space that's used by other family members, then you should keep your door ajar so they have access to it (for example, home office)... Obviously you don't want people walking into a catastrophic mess. It's nice to make the bed everyday & keep a handle on your clothes. (image below from In Style Home)
5) Keep the bathroom super-neat-- (I've been using the word "super" a lot lately because my 2-year old says food is "super hot" and it's now in my head.) Hang your towels neatly, keep your toiletries under control, close the lid on the commode after each use and if there's a squeegee, use it.
6) Be grateful-- this is pretty standard... It's nice to leave a little thank you note when you leave or send one when you get home.
7) And from
here, I found "Don't eat everything in sight." -- ah oops. hahahahah I KNOW I am guilty of this one!!! oh boy... (My in-laws get us this AMAZING prosciutto & salami & olives when we go there or when they visit, and I literally even eat it at breakfast time... the amount of consumption is incredible. And when my best friends & I visit each other, our purpose seems to be eating... But I guess this falls under the "non-guest" clause... I'm a non-guest when I'm there, right??)
8) In general, be easy & flexible.
9) AND.... On the Bed-making question I found this from
here: "MOST IMPORTANTLY: Leave the space ready for the next guest. The day you leave, strip the bed, place all soiled linens and towels neatly in pillow cases, and set the cases near the laundry facilities. Re-cover the bed with the bedspread so it will look fresh until the next guest arrives. Finally, check the space to be sure you haven’t left any personal items behind."
So, that's the answer to my big question... BUT I have to say, that as a HOST, I really like my guests to feel pampered & not do work. (Even non-guests!) I feel a twinge of guilt when they're working on the bed or trying to launder their linens/ towels. I just want them to relax & not worry about what they're leaving behind. If I ever see guests doing this or even making the bed, I tell them not to... so guests who get away with it in my house, have to do it before I see them trying ;)
That being said, I still do it when I'm at others' homes... (Again, usually being told by the host not to worry about it.) So will this always be one of those things that hosts and guests push each other on?? What do you think? What to you do as a guest? As a host? Is there any way we can set out a world-wide standard and just all agree on it??? Make a blog-world pact on how to do it & then spread it around ?!!!!) ;)
Live one day at a time
Less is more
Paring down makes you feel free... 
OK, all I can say about the entry in one of Martha Stewart's homes (above) is LOVE LOVE LOVE. I've been attracted to large-scale murals & etchings & toiles lately as you can see 
This one below from House Beautiful has been floating around a lot lately biut I just can't get over it. I love the shades of green against the warm, rich browns of the furniture. perfection.
Here's one found in a restaurant by frenchbutchic.blogspot.com:
SO GORGEOUS!!!! Here's another one, below:
The image below from 
Sometimes I strip the sheets & sort of remake it with the bedspread, and other times, I remake it (usually when the host says "Please don't do anything!") and there have even been times (Oh mother-in-law how I love you!!!- forgive me!!) that we've left the bed sort of messily thrown together but definitely not made (gasp!!) imagew below of my mother-in-law's guest room:
