Welcome to MDC!! And congrats on preparing yourself for TTC!
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I agree that prenatal vitamins are something you should start right away. They're just vitamins with some extra folic acid so there is no harm in taking them when not pregnant. And as ISISandOSIRIS said, they are recommended for all women of child bearing age b/c you never know when you might get pregnant and you want to build up your stores now. I take Rainbow Light one a day prenatals which you can usually find a your local natural food store.
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Getting off the pill is something you'll want to do ASAP if you want to TTC in 6 months b/c you really have no idea how long it will take your body to regulate again. Some women get pregnant ON the pill and others take up to a year to normalize again.  Definitely use back up after stopping the pill. I also second the recommendation from Vivica to read TCOYF and start charting your temp and cervical fluid. While it certainly is not necessary for everyone, it is really interesting, fun, and helps take the mystery out of what is happening with your body while TTC. Plus it can help you spot potential issues with your cycle and literally show you your body's post-BCP regulating process.
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There are a few other threads that have been started about how to prepare to TTC. I'll try and track them down and post them here...
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http://www.mothering.com/community/forum/thread/1312204/preparing-to-ttc-wwyd