If one purchases ready-made or semi-prepared food, the potential for kashrut problems greatly increases. Therefore, it is very important to be careful to buy products that have certification from a reliable kashrut agency, and likewise to eat only in restaurants that have a valid certificate of kashrut.

When purchasing food products that have undergone some form of preparation (cooking, preservation, etc.), one must take into consideration that various kashrut problems can apply to the main product and to its additives. Likewise, there may be issues with the manner in which the products were prepared; for example, whether they were cooked in non-kosher equipment or by gentiles. Therefore, one must make sure that the product has certification from a reliable kashrut agency. In restaurants, one should check to make sure that the kashrut certificate is current and has not expired.

Due to the many problems in the field of kashrut supervision, it is recommended to rely only on known, reputable kashrut authorities. One should also prefer restaurants that are managed by religiously observant people, who can be expected to feel personally responsible for the kashrut of the food that they serve their customers. A restaurant in which one can see a kashrut supervisor whose appearance and behavior indicate that he is a God-fearing individual is better than a restaurant with a certificate of kashrut on the wall, but which does not have a supervisor on site.

In some eateries, there are pictures of famous rabbis hanging on the walls, and there may also be charity boxes on the counter. Such religiously oriented items should not be viewed as an alternative to a proper kashrut certificate. Similarly, one should not rely on the word of the restaurant owner or the waiters, who state authoritatively that “everything is strictly kosher.” Instead, one should ask them to present a certified and up-to-date document of kashrut.