The way I buy a chair is by going to a store that sells them, and sitting for a few minutes in every one of them that looks even vaguely like it might be comfortable. I pick the ones that are the most comfortable, and sit there reading a book for a while. Salespeople sometimes stop by and ask what I'm doing, and I tell them I'm testing out the chairs. If they aren't happy with that, I'm happy with finding a different store, but that's only come up once.

It does you no good for me to tell you what I find comfortable to sit in. It has to be comfortable for you.

I've found that a half-hour in a chair is good enough to work out if it'll be comfortable enough for all day. Much less than that, and you're likely to miss something, like that it makes your legs go numb if you sit in it for half an hour.

Once I've found what I want, then I look at the pricetag, gasp, mutter under my breath about a few dollars of plastic and metal being sold for "how much!!!!?????!!!!!", and then buy it.

If I don't find one I like, or if the ones that are comfortable don't have the quality for a long use-life, I shop elsewhere.

Used office furniture stores are good. So is just about any place that sells chairs.