Every Jew, before selling ĥametz, should read the authorization contract he will be signing, so that he understands that he is empowering the rabbi to sell his ĥametz, and that the sale is absolute. Nonetheless, if instead of reading the contract one simply relied on the rabbi, the sale is valid, for, if the gentile comes during Pesaĥ to take the ĥametz, and the rabbi tells the Jew that the ĥametz indeed belongs to the gentile, and that he must give it to him, the Jew will do so.
The seller should write his name and address in clear script on the contract of sale so that the gentile knows who he is and where he lives. In this manner, the gentile buyer will be able, if he wants, to go to the seller’s house and take the ĥametz (see Sidur Pesaĥ Ke-hilkhato 11:7-8, and in the notes).
It is most preferable to give the gentile the key to the place where the ĥametz is located so that he can enter and take it at any time. In practice, though, it is sufficient to give the gentile the seller’s phone number so that when the gentile wants the ĥametz, he can call to come and take it. The most important principle is that sellers of ĥametz should be aware that after the sale, the ĥametz indeed belongs to the gentile, and the seller must allow him to enter the house and take his ĥametz (MB 448:12).
Ideally, the seller should indicate the various types of ĥametz, and their prices, on the contract the rabbi gives him to sign, and some people are meticulous about this. In practice, though, this is very difficult to carry out. Therefore, the custom is to write that all ĥametz in one’s possession is included in the sale, and that the price is in accordance with the accepted market price, as determined by appraisers (see BHL 448:3, s.v. “be-davar mu’at”).
It is best to write in the contract where exactly the ĥametz is located, for example: “In the upper left kitchen cupboard,” or “in the room on the right, in the box so marked.” Several places may be listed. Even without this, the sale is still valid, though all ĥametz should be gathered to one place and labeled. Everything gathered to the place determined for the sale by two hours before the onset of the prohibition against deriving benefit from ĥametz is included in the sale.
As noted, the preferred custom is to sell or rent to the gentile the place upon which the ĥametz rests, so that the ĥametz will be in the possession of the gentile, and the sale will appear to be like any other sale in which the buyer transfers possession.
One may sell ĥametz through a proxy who writes all relevant details and signs on the owner’s behalf. One may also sell ĥametz over the phone, by fax, or via the Internet. Usually, the person selling ĥametz signs and performs a kinyan (act of acquisition) in order to empower the rabbi as a shali’aĥ. Nonetheless, the kinyan is not crucial, as the most important thing is the transaction between the rabbi and the gentile, which is effective for everyone who has appointed the rabbi to sell his ĥametz (Sidur Pesaĥ Ke-hilkhato 19:4, 9-10).
In kitchens that belong to public institutions, the manager or his representative sells the ĥametz.
One should not sell the ĥametz that is absorbed into utensils. Quite a few laws relating to mekhirat ĥametz were introduced in order to make it clear to all that it is an actual sale, but if one writes that he is selling the ĥametz absorbed in his utensils, the sale will appear to be lacking seriousness, since ĥametz absorbed in utensils has no value and nobody is interested in buying ĥametz absorbed in utensils. The same applies to ĥametz stuck to utensils. Therefore, one should not indicate this in the sale contract.
. Sidur Pesaĥ Ke-hilkhato 11:12 states that one is permitted to enter into a ĥametz sale agreement with multiple rabbis. Even if each rabbi sells to a different gentile, the sale completed first takes effect. Preferably, one should not do this, since it seems deceitful, unless he is worried that one rabbi may not sell his ĥametz, and he wants to ensure that his ĥametz is sold one way or another.
Additionally, Sidur Pesaĥ Ke-hilkhato 11:20 states that if one was unable to sell his ĥametz due to some unavoidable reason, his friend may sell the ĥametz for him even without permission, since it is beneficial to the owner of the ĥametz, and one may act to benefit another even without permission. This is the opinion of many poskim, as cited in Piskei Teshuvot 448:21.
. Selling the utensils themselves to a gentile is not worthwhile, since after Pesaĥ one would be required to immerse the utensils in a mikveh, like any eating implement bought from a gentile (Ĥatam Sofer OĤ §109 and most poskim; however, AHS YD 108:52, states that one may be lenient). Therefore, some poskim write that it is preferable to sell the ĥametz that is absorbed in or stuck to the utensils, as written in Bedikat Ĥametz U-vi’uro 8:18-21. It is also written that one should only sell the utensils that have small holes or grooves, which make them difficult to clean, and that some are careful to sell the ĥametz that is absorbed in these utensils. The truth is, though, that this is unnecessary, because the ĥametz was already nullified. Even if there is substance remaining on the utensils, as long as there is less than a kezayit cumulatively, according to the majority of poskim there is no need to burn it (SAH 446 and Kuntrus Aĥaron 1). One must store these utensils in an enclosed area so that he does not accidentally use them on Pesaĥ, and after Pesaĥ one must remove any substance that remained on the utensils before using them, because of the rule that one may not benefit from ĥametz that he owned over Pesaĥ. Preferably, in order to satisfy those who maintain that one is required to burn even less than a kezayit of ĥametz (MA 442:12), one should remove any trace of ĥametz from the utensils before Pesaĥ, or ruin the residue with detergents until they are no longer fit for a dog’s consumption.
If this is the case, even if there is more than a kezayit, there is no obligation to burn it. Therefore, there is no need to sell the ĥametz that is stuck to the utensils, and even more so one should not sell the ĥametz that is absorbed in the utensils.