Each one of these funds operates under a different system and general philosophy. On arrival to Israel you will be required to join a fund within your first week in-country. You may change to a different fund only during the enrollment period and only if you have been in your existing fund at least 6 months. If you are working, you will pay for coverage directly from your paycheck. If not, go to any office of Bituach Leumi - National Insurance and register for payment of your health tax.
Children are free.
Kupot Holim Clalit Clalit is the oldest and largest health fund in Israel. They operate under a very strict HMO style policy. You may only use their doctors, clinics, hospitals and pharmacies. However, at many of their clinics and facilities, lines may be long and quality not always the highest. For the average American, the operational philosophy of Clalit will make them uncomfortable.