Hi Lostboy,
On the subject of catch and release; it is an entirely legitimate method. In fact almost all freshwater fishing in the UK is catch and release, to kill freshwater fish for the pot is frowned upon simply because many of the UK waterways (and therefore the inhabitants) are under immense pressure from both abstraction and pollution. Most of the fishable stretches of bank are controlled by clubs whose members act as guardians & conservationists for those areas. Sadly, this is a fact lost on the likes of PETA and similar misguided activists. Clearly the only reason these clubs exist is to allow their members to catch fish for sport, to remove fish for the pot only serves to denude the rivers further and is only likely to raise the hackles of local anglers (take the problems of Polish workers in the southeast who are often caught fishing without a net and with a lit disposable barbeque beside them! Just a question of cultural and national differences of opinion, but not all see it that way).
In England you'd be amazed at the care taken by anglers when fishing catch and release, hands should be wet and cooled before handling the fish (especially on sunny days), nets are always used (fishing to hand as it is called is really only carried out by match anglers these days, even then its rarely used). In the case of carp and pike anglers, large padded mats are used to prevent damage to the fish whilst they are being unhooked on the bank and specialist medicines used to treat any wounds caused by the hookhold. It all seems a little perverse, the care taken AFTER hooking and playing a fish and causing the distress, but its seen as sound practice to preserve the fishing for future generations. The upside for the fish is they usually get well fed and clean, secure environments to live out their lives.
With regard to unhooking fish; the use of a pair of forceps is recommended for predatory species (those with sharp gnashers), simply to put distance between your hands and the teeth. With barbed hooks a steady pressure in the opposite direction to entry usually results in a clean release, the wound can be treated in the case of freshwater fish or in saltwater simply return the fish. I personally wouldn't cut the line near the hook, in saltwater the hook will eventually rust out, in freshwater there is absolutely no chance that this will happen, period. You'll just leave a fish with a hook in it and potentially trailing line. Not good.
I often use a small pair of electricians pliers rather than forceps, they flex less and are easy to handle, however in the majority of cases I simply use my fingers.
As for Pike fishing, please do not use gags or the like to force the jaws open after capture, they are unnecessary, Pike require a method known as 'chinning' which is best left to anglers who have been taught how to do it simply because you need to slide your hand inside the mouth through a slit in the chin and apply a light pressure to the lower jaw in order to trigger a feeding reflex in the pike which makes its jaws drop open naturally. Treble hooks for catch and release Pike fishing should have two of the three barbs crushed down in order to allow easy unhooking. Personally I don't think trebles are necessary.
As mentioned before the best way to learn is join a club, there is so much to learn it can seem rather daunting and each type of fishing requires its own unique approach. As we are not talking survival here and you wish to use a handline I would say your fishing would be likely (legally) limited to sea fishing only.
Apologies for the lengthy post.