When I installed the new crankset on my Sofrider, I also installed dual-sided pedals. One side is your standard platform pedal that you can use with any shoes. The other side are for use with SPD cleats. Pedals like this are called clipless pedals because they do not have toe clips. While I completely understand that, I find it one of biking's big ironies that one clips into clipless pedals ("I clipped into my clipless pedals to go down to eat jumbo shrimp and other inedible cafeteria food.").
I've had the pedals, the cleats, and even the special shoes (to which one attaches the cleats) since well before I put the new crank on my bike. But it wasn't until today that I tried riding a bike using them. I'm very happy to report that everything went very well and I had no problems!
Somebody on the 'Bent Riders Online forum basically suggested that before riding clipped in, to find a pole to grab onto and practice repeatedly clipping into and out of the pedals (you remove your shoe from the pedal by twisting your heal outwards). I did that last night. At first, I had such a hard time clipping into the pedals, I took one of my shoes off and just clipped it into the pedal a few times. After that, I spent about 20 minutes sitting on my bike, holding a pole in my garage repeatedly clipping into and out of the pedals.
The general idea is that before starting, you clip in one foot (always my right foot) before taking the other foot off of the ground. The hard part is getting the second foot clipped in. It turns out (as I found out this morning) that it is actually easier to do this pedaling than it is holding a pole in ones garage.
On my way to work, I got a twig stuck in my wheel. I thought that I might have a flat, so I downshifted, unclipped, and stopped. After I removed the stick, I even managed to start back up on a hill of about 5% incline without falling over. Not too shabby.
The biggest advantage of clipping into pedals (and some extent, toe clips) is that in addition to propelling the bicycle by pushing on the pedals, you can now also propel the bike by pulling on the pedals. One thing I learned today (and, well, this is pretty obvious), after spending years of pedaling without being firmly attached to the pedals, I'm very used to pushing on the pedals and not at all used to pulling on them. I can do it, and it helps me pick up speed a lot, but it doesn't yet feel very natural and I can't do it for very long.
The other big difference is that now that my feet are attached to the pedals, I feel much more in control when I'm spinning - pedaling at a high cadence or RPM. Without clipping in, I find that I feel like the bike gets out of control at a high spinning rate. With the pedals, everything is much smoother. Very nice. This is probably obvious and I was hoping that something like this would happen, but I was very pleasantly surprised at how big an effect it is.