I have ADHD too and most of the time struggle to keep that monster at bay. I've learnt to keep my focus in many other areas in my life, but with IM I find it difficult to keep my focus and attention on one and not jumping to another. How do you keep your focus/attention in IM?
Break things into smaller groups of tasks
Don't start anything else till the current group of tasks is complete.
Write down the task-list