Nap Schedule

My 8-month-old has a pretty unpredictable nap schedule. She generally takes two good naps a day - one in the morning and one in the afternoon- plus a short nap in the evening, but sometimes she'll do four short naps. And the times for all naps vary. Sometimes she'll nap at 8 in the morning; other days she'll nap at 10. Makes it hard to plan my life when I'm not sure when she's going to be willing/able to sleep. We've got her on a fairly consistent nighttime schedule - bed at 8, up around 7 - but naps are kind of driving me crazy. I hear about these babies who nap every day at about the same time. What can I do to help her establish a regular nap schedule?