One of the great joys about working at home is the freedom to be flexible about what you do and when.
I would set yourself some 'rules' - i.e. I am not going to work later than 6, or not at the weekend, or not before 9,30 - whatever makes sense to you - and then make sure that you stick to that.
I try and break up my day a little, otherwise it's too boring/intense. Plus, I have shoulder/neck problems and I have been told by my osteopath not to sit in the same position/at the PC for longer than 20 minutes. I try and follow that, but it's not always practical. But just getting up to go to the loo/get a drink can be helpful
I am an inveterate list maker. Post-its make little A5 'things to do' pads and these are fab. I have one for each project I'm working on, one for me labelled 'personal' and one labelled 'home' for all the domestic stuff. They are all stuck on the wall next to me, and there are little boxes to tick off all the things you have done.
A really good time management technique is to look at all the things on all your lists (assuming you've got that far!) and prioritise them, then write yourself a list for that day in order of priority. If you can or need to, put times against each one and work out how long it's going to take you to do it. Printing out a daily page from Outlook can be helpful here as you can schedule things in that way.
But if you do this, make sure that you also plan in breaks, rests, time to MN, time to cook, time to go for a walk - whatever - otherwise these lists will become your slavedriver rather than your helper.
(I'd love to have a job coming and helping people get organised actually - I'm so anal!)