The commandment of visiting the sick (Bikur Cholim) is a very great commandment. Concerning this mitzvah it states in the Mishnah that this is one of those deeds that one "eats of its fruits" in this world and retains the "principal" in the next world.
According to certain opinions this is a biblical mitzvah based upon the verse "And you shall walk in His ways"1. According to others (including Maimonides) it is a rabbinical commandment. Yet others maintain that this is a mitzvah which is a law that was handed down to Moses at Sinai (Halacha LeMoshe Misinai). Yet, Maimonides also states that the commandment of visiting the sick is also an aspect of the mitzvah of "You shall love your fellow as yourself" (VeHoavta lerei'acha komocho).
• There is no limit to the amount of times or level that one can fulfill this commandment, provided one does not become too bothersome for the sick person. Most of the time a short visit is preferable. One needs to take the status and the desires of the sick into considerations.
• One should not limit one's visits just to one who is older and/or greater than he is. One needs to visit even those younger than him or not as great as he is.
• If for example there are two sick patients, one who has many visitors and the second a few or none, one should preferably visit the person who has a few or no visitors.
• Opinions vary whether one should visit a person whom he hates. According to some, he should avoid visiting since it may appear as if he is rejoicing over the other's illness. The best thing is to inform the sick person through a third party that he would like to visit him. If it is acceptable to the patient, he may visit him, for this may be the beginning of a peace process.
• No blessing is said when performing the commandment of visiting the sick.
• Not all patients are in a position to receive visitors. Under such circumstances one should inquire of the relatives if it is okay to visit and even then one should try to keep the visit short. One needs to also have a sixth sense and realize when he is overstaying. In a situation where a patient is not ready for visitors, one can still visit by staying in the foyer or hallway and helping out family members or say Psalms on behalf of the person.
• Although most aspects of visiting the sick can be fulfilled only with a personal visit, if one is not able to do a personal visit, he can fulfill the mitzvah with a phone call.
• One should enter the room of the sick in a positive mood and feeling. One should not display any moods of sadness or melancholy as this could affect the welfare of the patient.
• One should not bring bad tiding to a sick person.
• If one needs to fulfill the commandment of visiting the sick and consoling a mourner (Nichum Aveilim) and he is able to just do one or the other, then preference is given to the mitzvah of consoling a mourner.
• Rabbi Yeshayahu Horowitz, the holy Shelah, writes that the commandment of visiting the sick involves three components, 1. with one's body (beguf), 2. with one's soul (benefesh) and 3. with one's money (bemamon).
With one's body -- Not only should one pay a personal visit, but one should also do actual things which will uplift the spirit and the comfort of the sick. This can be accomplished in a number of ways; bringing him material to read, bringing him food (especially if the patient is in a hospital where the patients might avoid eating many of the foods due to kashrut concerns, helping raise or lower the bed for him, brighten up the room, etc. When a patient is in a hospital there are more opportunities for doing this aspect, since nurses do not always have enough time to deal with patients. [As mentioned earlier one must use common sense and not overstay a visit or visit at inopportune times.
With one's soul -- by praying and saying Psalms for the sick. One must not forget to wish and bless the sick with a speedy recovery ("refuah shleimah") before leaving. Rabbi Moshe Isserlis, the Rama, writes that if ones visits the sick and does not pray for him has not fulfilled the commandment of visiting the sick. The Talmud2 states that if one is able to pray for the sick and does not is called a sinner. [Thus, if Psalms is being said in synagogue for a sick person, it is important to participate.]
With one's money -- If the sick person is having financial difficulties covering his medical expenses, then one should help him. This also will help bring the sick person a bit of peace of mind. [It would seem to me that included in this component would be giving charity on behalf of the sick person.]