Speeches
The reason why speeches are of such import is that all people understand that a Bar-Mitzva is hopefully the beginning of the boys practice of Mitzvot and he should start it with the proper footing. A learned speech is therefore most appropriate.
Others have the custom that the lad makes a speech during the feast, which was the custom in Vermaisa. Still others have done away with the custom all together so as not to embarrass those youth who are not learned, also in order to avoid arguments if their are two Bar-Mitzvahs.
Rivkind points out that the speeches were never given in Hebrew but were always in the spoken languages The texts were published in Hebrew so all could benefit. He further says that with the advent of Zionism many people speak in Hebrew.
Rivkind and others discussed at length many different nuances of this custom in all of the different Jewish communities. I will cite some of them here.
In making the speech in the synagogue their are many different places it occupied during the service some said it in between Ashrei and Uba Letzion, others just after the boys Aliya before the next person would go up. Probably the most popular time was on Shabbot after returning the Torah, since in many places this is when the rabbi delivers his sermon.