1. Do carry plastic ponchos.
2. if it is just sprinkling, generally carry on as if nothing is happening. Thank Tinkerbell for sprinkling a little pixie dust on to cool things down. Laugh!
3. In a downpour, if possible, wait it out. Unless you are late for an ADR or FP, try and seek cover for about ten minutes. Very often, that's enough. Then you have saved yourself a poncho and the effort. We like to call late afternoon, thunderstorm o'clock! That's usually when they happen. Before, the humidity and temps build...after the air usually cools quite a bit. If you understand that, you can use it to your touring advantage.
4. Do look at the weather report each day. Or rather the radar. 48 hours out it too far, but each morning, you can often get a sense of rain that's going to be short downbursts, or heavy rain that will last half the day or more. Having a good weather app on your phone helps.
5. In addition to ponchos, sometimes a rain jacket is better. We used ponchos if the rain 5 is 40% or less. Jackets if it is higher.
6. Do NOT wear sneakers on wet days! Water tolerant shoes are your friend. Something like Tevas, or even the dreaded
Crocs can be a great investment at WDW! What's nice about Crocs is that your foot doesn't slide around. Sometimes flip flops can be dangerously slippery. Some are not, but many are. Quality footwear is essential, IMO. Two pairs. Old sneakers that get wet smell horrible, take days to dry. I mean everyone within 20 feet can smell your feet!
7. If all else fails, there's a great outlet mall just off I-4.
8. Light crowds can be an advantage. Other times, rain can be a pain. EVC's are not supposed to be out in rain, for one.
9. Remember that half of AK closes during thunder. I try to plan so AK days can be swapped. (If we have an ADR on our AK day, it is at a resort).
10.

It is probably good to remember to take the poncho off when the rain stops. I always see folks baking in the sun under their plastic coating hours after the 10minute rain ended. I just can't imagine it's enjoyable when it's 90 degrees!