Well they say if your fasting bg levels fluctuate by more than 1.7mmol you need to adjust your basal rates, but this may be too much for some people and its probably better to have your own target.
TBH I wouldn't test basal rates by missing two consecutive meals, better to do one at a time (if this is what you mean above) and test hourly, I started on a pump a few months ago and now have 7 different basal rates.