So you need to wash your lolita finery? Huh, who'd have thought you'd need to wash clothes, am I right? But it isn't really hard at all. I'll start off with the general rules:
1) Aim to wash your clothing as infrequently as possible. This is easier in winter by the way. But the fewer times you wash it the less things are going to be beat up by being washed. And if it isn't touching your skin and you aren't glistening like a star then you can normally get at least a few wears out of something like a skirt or jsk. I haven't actually washed my very favorite Victorian Maiden skirt yet. I got it in 2009, so that's about 3 years and I'd estimate about 30-40 wears. But it doesn't smell or feel weird or have any other noticeable sign of wear (I've cursed myself to spill something on it now you realize). So it hangs in my closet, happy as a clam. I don't quite follow the maxim of waiting til your pants stand up and walk themselves to the washing machine but I'm no longer a one wear kind of gal (except on certain things like socks and blouses in the summer).
2) You either are or aren't a fan of spot cleaning and I, actually, am not. I know the difference in fade is minute and people can't see it but every time you clean something you are damaging it. I'm a curator, I've had to deal with a historic wardrobe (and other textiles) and let me tell you every time you clean something you damage it. But even with historic objects you still have to clean them because there is greater damage done by not doing so every so often. And if we're talking something really delicate or finicky then yes spot treating is the way to go. But I tend to not like to wear such delicate things as then I'm more worried about my clothes than having fun.
3) If you can smell it or know there is a sweat stain then clean it soon. That blouse you wore out in 100 degree heat and 100% humidity so you were glistening like a diamond? You're going to want to wash that. Soon. Sweat is very hard on clothing, you don't want it chilling on there for like a month. The longer it is on there the more likely it is to stain or cause more serious damage. Ideally you want to wash the sweat out before it even dries but obviously that isn't necessarily possible every time. Just make sure that whatever it is like that makes it into your weekly/bi-weekly/monthly wash.
When it comes to detergent, use sparingly. As my momma said, it is always better to not quite have enough detergent than to not be able to rinse all the detergent out. I always make sure I fill the cap under the line I'm shooting for or just default to the medium load line. Everything comes out fresh as a daisy and not overly sudsed.
Now as for what garments need what kind of care...
Toss it in the wash (delicate bag would be awesome but not required):
Skirts/JSKs/OPs with few details or that otherwise seem hardy and hale
Delicate Bag/Pillow Case required:
Skirts/JSKs/OPs that you are kind of worried about, so lots of delicate trim or a delicate fabric. Or that you're just paranoid about. It is okay to be paranoid about them, better paranoid than with a destroyed dress.
Check the internet:
Prints. Check the web to see if someone else has washed it before and if so how they did it and how that went.
Alright, with that said, let's begin!
I normally just toss my bloomers, blouses, petticoats and Bodyline into whatever color wash they match. So white eyelet bloomers and cream AatP socks with pink/green floral design go in the light/white load. and my navy petticoat and black Antique Clock skirt go in the dark/black load. I don't own a brand blouse but I own plenty with lots of delicate lace and pin tucks and god the ruffles. And they all do well just tossed in (though two are a very delicate material and they get a pillow case together). Turn everything inside out by the way. It helps to protect the outer of the fabric so your clothes will last longer (and the inner which is closer to your skin will get a more thorough washing).
Now for things which you're worried about, here is a super simple way to make sure they survive the wash. Please note if something is particularly dirty then this isn't tops. You may want to hand wash in a sink to get most/all of the grime off. You can toss it in a pillow case without rinsing and toss it into the regular wash if you don't feel like spending an hour rinsing, this is what I do.