Some characters have multiple pronunciations (多音字), but often some pronunciations are much more common. For example, 吗 is almost always used as a question particle pronounced ma, but occasionally it is pronounced mǎ (as in 吗啡 [morphine]) or má (in the phrase 干吗).
Most dictionaries will show the different pronunciations and their corresponding definitions, but there is no way to tell which ones are the most frequent. Are there any sources that show the relative frequency of 多音字?