Have you ever seen someone doing yard work in dress clothes, in the dark? No? Well, you haven't been in my neighborhood lately. Yes, I have been known to do some tree trimming or weed pulling in heels and after sunset...why you ask? Because that is when I thought about it!
Life is busy for everyone, and some times when I find a moment to squeeze an unexpected task in, I go for it. Yes, that can lead to some strange timing, but, if it means that I was able to accomplish more than I thought that day, who cares?
I subscribe to the "do it when you think of it", and "keep it in front of your eyes" theories. This may mean that I place an empty 2 liter bottle of my Diet Coke on my counter rather than the recycling when I am done with it. This way it is visible and reminds me to put a new one in the fridge so I have cold soda ready for me when I want it.
The next time you run out of shampoo, don't throw it away! Keep it out until you remember to replace it with a new one, etc., etc.
My husband has learned that I always do things for a reason, so he doesn't question me (as much) any more when he finds random things placed in strange areas of the house. He knows that it was on purpose, to remind me to take care of something that I thought I would forget.
Now, this does work, in large part, because I don't have a cluttered house. If you have a lot out on counters already, this won't work as well for you!
Another "trick" that I use is my phone. Have you ever been lying in bed and suddenly remembered a task or appointment for the next day? Then, you find you can't sleep because you are trying to not forget it again? Pick up the phone, put it in your calendar, with an alarm reminder, and get some sleep!
By keeping things in front of your eyes and doing them when you think of it, you may find yourself catching up on more of those, "I've been meaning too..." items.