Switching formulas?

How do you safely change your baby's formula? Right now he's supplimenting with Earth's Best Organic Sensitivity, but we're going to switch to Similac Alimentum Ready to Feed (liquid) and I'm unsure how to do it...

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About Jamie
Current: Gresham, Oregon
Birth: March 22
On Moms.com since: Mar 7, 2014
I am a stay at home to a handsome baby boy. He's my first and possibly my only one...
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