Find a vision. See how you want your home (or whatever you are organizing) and write it down. Don't just think about it, but feel it. Know how you want your home to feel and look. Envision what you are going to accomplish.
 Write down small and larger goals that will get you to your vision. If you are doing a whole house break it down by rooms, then have lists for each room too. Let the small goals work together to accomplish the big goal. As you start working, think of the end result and not the actual work to get there.
 Make sure you have the right attitude. This means you need to think positive, no more negative. Negative thoughts like "I will never be organized" stop right here. Change your thinking to "I am on my way to organized!" and you will get a lot farther. For motivation in any aspect of your life what you really need is positive thinking.
 Develop a system of organization before you start. Decide how you will organize everything, if the decision is made beforehand then you know what you are going into and you won't get stressed out. A system will make everything run smoothly while you are organizing and it will help you keep organized after too.
 If you are struggling to want to take on the task alone, find a buddy. Get someone else that can come and help you. They will keep you on track and also help you get it done a little faster. Plus, the company can help you forget about all of the hard work you are doing.
 Maybe you keep talking about getting organized but say you don't have the right stuff. Get the right stuff. Go out and buy shelves, boxes, or whatever to get your stuff organized. Once you have made an investment into it then you will know you have to finish it. Plus, if you are buying large tubs or boxes then they are going to be in the way until you do something with them.
 Don't think that you need to tackle every part of your life at once. If you try to do everything at once then you will be overwhelmed and never get anywhere. Let your goals lead into one another and get the overall done, but only be focused on your immediate goal.
 Remember that your goal isn't to have perfection, it is to be organized in such a way as to have efficiency. So if your system doesn't make everything look perfect, but you can find it right away, then you have accomplished your task. You are trying to make your life easier with organization, so put everything where you will remember where to find it. Don't make it over complicated.

Any of these can serve as motivation, they can help you know where to start and what to expect. Getting organized doesn't have to take over your life, but it should enhance it over all. If you can get started, you can finish.