Pick a room of the house, any room. Don't worry about which one because trust me you will want to get through them all soon enough.
Get a box or basket, laundry baskets work perfectly. Open up the room one space at a time and look and see what you have in there. Open up those drawers and cupboards and dig deep into the depths of the unknown leaving no place un-touched. You might want to have various baskets. One for trash, one for charity, one for the "I'm not sure" pile and one "to do" pile.
Pick up something. Ask yourself, Do I use this? Will I use it? Why am I keeping it? Can I give it away to charity? Can I sell it? Do I need to return it? Do I have duplicates of this? Does it fit? Is it broken? Can it be repaired? and am I wasting my space and time with it?
Dispose. Go on do it! I dare you! Try and be brutal, the more you are the easier it will get. If you are really unsure about what to do with an item put it in the "I'm not sure" pile and you can think about it for 3 months (at the most). Give anything that is staying a home and note it mentally, this will help you know what you have, where it belongs and will help you with your speed cleans.(blog coming soon).
Finalise the room by actually throwing out the items you need to, actually put the items to be donated in your car and actually put the "I'm not sure items" somewhere you can't see or use them. Remember set yourself a reminder for 3 months and any items you have not touched or thought about are to be culled. If you have anything that need to be repaired or given back to a friend make an "to do" box and put it somewhere you will see everyday (close to the living area or front door works well) this will encourage you to actually deal with it, rather than it making its way back into the depths.
Admire. Check out how much space you have, You will notice that you have less to clean and less to worry about. The feeling is addictive.
Now I'm not suggesting you go crazy here and burn yourself out but maybe do this to one room once every couple of weeks and work your way around the house. Pause for a few months or until a change of season and go again. Trust me you will love it.