There are differing schools of thought that have been discussed at length in other threads. The approach that works for me is to use layering and ventilation to keep me reasonably dry. Layers, zippers and wool/tech fabrics are your friends. Bulk, lack of ventilation, and cotton are your enemies. The key is to find the appropriate combination of layers, ventilation and fabric that will keep you comfortably cool to minimize perspiration and then wick it away from the skin. I usually start with just enough layers that I feel rather cool but not cold starting out. The exception is feet and hands which should stay dry and warm as much as possible. I have a rear rack on which I carry an extra layer for added warmth if it is needed, or where I can stash layers that I need to peel after I'm warmed up.
I'm not going into detail on every combination that I wear for each possible riding condition, but as an example, during a cold and windy century this fall I wore a tech fabric base layer, a 1/2 zip long-sleeve tech fabric jersey, a full zip fleece vest and a tech fabric jacket with a hood that can be pulled up over my helmet. On my back rack was a waterproof stuff sack with a windbreaker. It was quite cold in the morning and I was rather cool but not shivering while riding through rolling hills and into a headwind. As I warmed up I would unzip the jacket and vest as needed so that I stayed cool but comfortable. Later the sun finally came out and I started warming up. I eventually put the jacket into the stuff sack and was riding with the vest about 3/4 unzipped and the jersey about 1/4 unzipped. I was also able to swap from winter gloves to regular fingerless riding gloves. I never really got warm and felt cool but comfortable throughout the ride. When we got back to the school where the ride originated, I went to change clothes in the men's locker room. My baselayer was damp in the middle of my chest and armpits and dry everywhere else. The jersey was for the most part dry. Now, I'm a clydesdale and a heavy sweater, almost embarassingly so at the gym or other indoor athletics. My effort that day had ranged from moderate to pushing pretty hard uphill into a 15+ mph wind. So thermal regulation is possible and you can control how much you perspire.
I have had people tell me "It doesn't matter what I wear I sweat so that I'm soaked no matter what." My question in reply is "Would you be sweating if you were naked under the same conditions?" The usual response is "no" so my advice is to find appropriate layering somewhere between being naked and what you are wearing now. If you are warm enough not to shiver and cool enough not to sweat excessively, you got it right. You are likely going to have to shed layers or make other adjustments as conditions change and you warm up during your ride. Make adjustments early rather than letting your base layer get soaked.
Last edited by Myosmith; 11-22-12 at 11:25 PM.