I'm lucky I have a office which I have my work computer set up with extra screens, docking station etc... I realise it's not possible for everyone to work like this as you might have to double up the kitchen table as your desk. However do work where possible at some kind of desk. I also suffer really badly with back issues from time to time as many people do, so you may want an adjustable chair. I can't stress enough how much a good chair can support you and save you a fortune in Chiropractor fees down the line!
Don't sit in bed, or sit on the sofa. Unless you work for some kind of start up in Shoreditch you probably don't work sat at sofa in the office - so why would you at home. It's about being focused whilst you are at home. Sat doing the emails whilst watching homes under the hammer isn't probably going to be that productive....