I am by no means an IT person, but I will to try to answer your questions to the best of my knowledge. Others can chime in to correct me if I am mistaken.
The most effective filter depends on how you define effective. The most restrictive will probably be a whitelist program that works on the ISP level. What type of filter you get should depend on you internet needs and the ages of those that use your computer.
White list filers allow access only to sites that are deemed to be “good”, while blocking everything else. Black list filters allow access to everything but denies access to sites that are deemed “bad”. Most blacklist filters have a list that is regularly updated on sites that have content that need to be disallowed.
ISP filters do the filtering at(as you guessed) the ISP level. So any devices trying to connect to your internet line will be filtered. This includes all computers, tablets and ipads you may have, as well as nosy neighbors. Local filters will only work on the device you install them on.
To receive ISP filtering you need to get your internet from a provider that will filter your internet. Most ISP’s offer such a service. Check with your provider for price and exactly what is filtered. Then compare to Jewish filters and again decide which is better suited for your needs.
There are numerous filters on the market, too many to name. Some off the top of my head are: NetNanny, SafeEyes, and K9. Also most antivirus programs have filtering capabilities as well, so you don’t need two programs running on your computer.
Smart phones pose a unique challenge for filtering programs do to the nature of the mobile websites and the amount of memory in the phone. Some companies will give you a special browser that will only allow certain sites. I’m not sure how well they work.
Hope this helps!