If you're pretty serious about keeping your paint looking good, you have to adopt a good washing technique. Washing is where the majority of marring and scratching occurs. (Marring is like light scratches that show up in the sunlight)
If your vehicle is pretty dirty try the Two Bucket method if you want to safely get it clean. One bucket for rinse water and one for soapy water. First you put the mitt in the soapy water and then wash an area maybe half the size of your hood, then put the mitt in the rinse water bucket and slosh it up and down. This will get the dirt out, and keep your soapy water much cleaner, and less likely to put microscratches in your paint.
You always want to keep your wash water as clean and soapy as possible. Lubrication is the key to keeping your paint mar-free, especially with the soft paint that newer Toyota's seem to have.
I recommend that you use a large "fluffy" chenille or Sheepskin mitt. They will hold a large amount of soap and water.