On 5 April 1803 Beethoven conducted an concert of his own works: the First and Second Symphonies; The Third Piano Concerto, and his oratorio Christ on the Mount of Olives. It is likely that the he directed the piano concerto (which he played) from the piano. Ignaz von Seyfried gave an account of Beethoven’s conducting technique:
Our master could not be presented as a model in respect of conducting, and the orchestra always had to have a care in order not to be led astray by its mentor; for he had ears only for his composition and was ceaselessly occupied by manifold gesticulations to indicate the desired expression. He often made a down beat for an accent in the wrong place. He used to suggest a diminuendo by crouching down more and more, and at a pianissimo he would almost creep under the desk. When the volume of the sound grew he rose up also as if out of a stage-trap, and with the entrance of the power of the band he would stand upon the tips of his toes almost as big as a giant, and waving his arms, seemed about to soar upwards to the skies. Everything about him was active, not a bit of his organism idle, and the man was comparable to a perpetuum mobile. He did not belong to those capricious composers whom no orchestra in the world can satisfy. At times, indeed, he was altogether too considerate and did not even repeat passages which went badly at rehearsal: “It will go better next time,” he would say. He was very particular about expression, the delicate nuances, the equable distribution of light and shade as well as an effective tempo rubato, and without betraying vexation, would discuss them with the individual players. When he observed that the players would enter into his intentions and play together with increasing ardor, inspired by the magical power of his creations, his face would be transfigured with joy, all his features beamed with pleasure, and satisfaction, a pleased smile would play around hi lips and a thundering “Bravi tutti!” reward the successful achievement. It was the first and loftiest triumphal moment for the genius, compared with which, as he confessed ,the tempestuous applause of a receptive audience was as nothing. When playing at first sight, there were frequent pauses for the purpose of correcting the parts and then the thread would be broken; but he was patient even then; but when things went to pieces, particularly in the scherzos of his symphonies at a sudden and unexpected change of rhythm, he would shout with laughter and say he had expected nothing else, but was reckoning on it from the beginning; he was almost childishly glad that he had been successful in “unhorsing such excellent riders”.
Thayer, Alexander Wheelock, Elliot Forbes, ed. (1964) The Life of Beethoven, Princeton. Cited in: Marek, George (1969) Beethoven: Biography of a Genius. London: William Kimber, p.336-337.