Your first instinct will be to add the prospects that offer you the greatest actual revenue or profit. You'll want to put these clients on the list because you stand to gain the most in the way of attaining your quota and, of course, increasing your commission. These are very real and excellent reasons to add these prospects to the list, but don't add them yet.
The next group you might naturally try to put on your dream list will be those prospects that are highly visible. These are the prospects that all of your competitors have on their lists. These prospects give you visibility and credibility, two more great reasons to add them to the list. But this still isn't the list that I want you write.
The list I want you to write is the real list of dream clients. This list is going to be made up of the prospects who would be made a better, more competitive company within their own marketplace by choosing to work with you. These are the prospects that you are willing to go to the mat with, bringing your A-game to the relationship to ensure their success. These are the prospects that will challenge you to grow as a sales professional, and who will challenge your company to be the best that it can be. This list will generate the long-term relationships on which your sales and your companies success can be built.
Make your list. Then, let me know if you don't find it much easier to approach and win these clients after you have discovered for yourself your real motivations. And, you can still add the first two groups to the list, but you might find you want to put them a little further from the top.