1. Detox. When you switch from anti-perspirant your glands detox out all the gland clogging stuff. For some people this means really bad odor, and for others it shows up as stains.
2. Oils & Waxes. Most people only need a thin layer of our deodorant, like 1 or 2 swipes, so don't apply more than you need. Normally staining isn't an issue, especially if your laundry detergent normally does well with grease (think oil splatters while cooking or dripping greasy food on your clothes). We use Shout Advanced Ultra Concentrated Gel if we spill large amounts of deodorant on our clothes while making it and that works really well for getting HUGE deodorant stains out.
Hope that helps!