Tatia - Annie pretty much described what my neuro told me to do when I first started Mestinon.

1/4 Tablet (15mg) every four hours - - regardless of whether you are strong or weak for at least five days.
If weak, make a note of how long it was since your last pill - but don't change the plan

After 5 days, it everything was pretty good, then stay on this dose.
But, if you noted that you experienced weakness in between doses; then take 1/2 tablet (30mg) every four hours. Again note if /when weakness is experienced in between doses. And, as before, do this for 5 days.

At this point, I was told to call in and report how things were going. My neuro has always emphasized consistency...settle on a dose and stick with it every 4 hours. Until you have established a baseline (so to speak), it is really counterproductive to experiment.

Good luck....and if things are really crazy and not right...call neuros office. You might not get to talk to neuro, but (in my case) the PA or nurse always gets back to me within a 24 hours on any questions I have.