On the first two days of Sukkos, one must own the set of Daled Minim he uses to perform the Mitzvah. [However, one may use a borrowed set for Hallel and Hosha’anos.]
When giving the Daled Minim to someone over the age of Bar Mitzvah, one should expressly state that it is a “Matono Al M’nas Lehachzir”; i.e. a gift conditional on its return. This is especially important on the first day of Sukkos. [If one neglected to say this, it is still the presumed intention – provided that the giver and recipient are both aware that one must own the set of Daled Minim.]
There is a dispute as to whether a woman must own the Daled Minim in order to recite a Brocho. It is therefore preferable that it be given to her as a “Matono Al M’nas Lehachzir”. [Halachically, items given to a married woman normally become the property of her husband. Nevertheless, the Daled Minim are still regarded as hers, since it is obvious that it was given to her on condition that it does not become her husband’s.]
As mentioned earlier, a boy of the age of Chinuch is required to bentch Lulav. According to many Rishonim, the Mitzvah of Chinuch requires him to own the set he uses. At the same time, a boy under Bar Mitzvah has the ability to acquire, but not to give back. Therefore, one should not give the Daled Minim to a child as a “Matono Al M’nas Lehachzir”. Rather, the father should purchase a set of Daled Minim for him.
If this is impractical or beyond one’s means, one may rely on the Rishonim who do not require a boy under Bar Mitzvah to own the set he uses. In this case, the owner of the Daled Minim should hold the boy’s hands or the Lulav while the Brocho is made, intending not to give it to him. [Technically, another solution is to give the Daled Minim to the boy only after the adults have bentched Lulav. However, this is not a practical solution if the Daled Minim will be used later for Mivtzoim, or if one has several boys. Furthermore, some opinions hold that the Daled Minim must be owned on the second day of Sukkos as well, which is a problem if it was given to a boy on the first day.]