If you're like me, you often stay in bed until you really need to get up and going which cuts down on prep-time. When you're late, it seems like the water takes forever to warm up. While you could use the time to brush your teeth, rinse with some mouthwash, or any number of other things, here's a tip to help move along your morning routine and cut down wasted time if all you want is a seriously fast shower.
While the water is still cold, just wet your head down and hold it over the shower (assuming you have a tub type shower). Your head generally can take the icy cold, death water when it would not be comfortable hopping in completely. With your head wet, you can now carefully apply shampoo and by the time you're ready to rinse your head, you can climb in the tub and get clean.
If you're really desperate and your shower takes seriously forever, you could even start to suds up with soap so all you have to do is hop in, rinse off, and hop out. Then again, if your water takes that long, you might want to check on your plumbing.
Short version: You don't need to wait for the water to be hot to start shampooing.