1. Reclining [at the Seder] is not to be done with the person lying on his back or face down since this is not a manner of freedom. Nor should one recline on his right side because he will need his right hand to hold the food he is eating which would be impossible if he is resting on it] and so that the food not go down the windpipe (trachea) instead of the gullet (esophagus). Therefore, one should recline on his left side. Even a left-handed person should lean on his left side; however, after the fact, if a left-handed person leaned on his right side, he fulfilled his obligation (Shulchan Aruchand Mishnah Berurah 472).
2. When reclining, one needs to be leaning on a surface such as the bed or bench. After the fact, if one leaned on another person sitting to his side, it is a valid reclining. But if one reclined on his own knees, this is not considered reclining, as it appears as though he is worrying (ibid.).
