Carb ice can certainly occur when not expected, taxiing included. The comments suggesting a reference to the POH are obviously the best to follow. Do remember that not only does the use of carb heat cause a slight loss of power, but to be the most effective, it is vital to lean/relean the engine after application, the obtain the greatest effect. If you actually need the carb heat to deice the carb, the engine may already be running a little more rich than is intended, due to restricted airflow. When you select carb heat, you introduce hooter air, which is less dense (similar to a higher altitude), so less power. Less power equals less exhaust gass temperature, which is the source of heat for the carb heat in the first place. So, to get the heat back, lean the engine. That will increase the EGT again, and you'll get much hotter air, and thus more effective carb heat.
Also, my certification testing of several carb heat systems, including my Cessna 150, indicates that if you really have to get rid of ice in the carb in flight, the very best result will be attained with a power setting much less than full power. I attribute this to the lower mass airflow through the exhaust heat exchanger and carb, which allows the air to heat up more, and carry more of that heat to the offending carb ice. This reduced power setting also allows many engines to be operated at, or beyond peak lean without damage (consult you engine's manual please). Therefore, without an exhaust gas temperature gauge, you can lean for heating effect simply by bringing the mixture toward lean until the engine stumbles, then richening it a little (with carb heat already hot).
In my 150, an RPM of about 2100 and peak lean with carb heat hot gives the best result (I have a carb air temperature gauge). Incresing power fromthis setting will result in coller carb air temperatures, thus, one would presume, less effective carb deicing.
Also be cautious that the use of carb heat as a preventative measure, can create a different problem. If the moisture in the air is just below freezing (yes, you can have water drops in air which is jut below freezing), and the carb air temperature is also less than freezing, there is a chance that the water will go right through the carb without interfering with the way the engine ran. If you apply carb heat, you can warm the moisture, which then may refreeze in the carb. I have been able to produce this effect at times. In this case, carb heat cold would have been safer.
Also remember that the use of carb heat on the ground removes the air filter from the induction air circuit (on purpose), thus if it is dusty, that's wht's going through your engine. It is agreed though that dusty and moist do not usually occur at the same time in air.
For what it's worth, I (while using a carb air temperature gauge) never use carb heat, inless it's use is indicated by the conditions. I check it's working, and that's it. Only in moist conditions, when the carb air is right around freezing do I apply carb heat, and then only enough to bring the carb air up out of the freezing range.
The application of carb heat will not cause harmful detonation in the engine, if it is otherwise being run properly (correct octane gasoline and not over square for normaly aspirated engines)
Pilot DAR