You can find detailed guides for fishing - both for members and for free-to-play - and similar guides for other skills, at online sites such as runescape.wikia.com or others.
start off by going to the fishing shop north west of the lumbridge castle and getting a free crayfish cage, then there should be a fishing spot north west of the shop.
The best way to fish on runescape is to use a net or a fishing rod and bait in draynor. Then it is easy to bank your fish
On the pier in Karamaja ;)
Raw fish.
From Runescape Wikia: "The Cavefish are a type of fish that can only be found in the Living Rock Caverns. The Living Rock Caverns can be found underneath the Dwarven Mine..."
There are various spots throughout all of runescape you can harpoon fish, the main ones are catherby, the fishing guild, and the island of karajama
Bass is a members only fish, only members can fish it.
no
Rocktail
80+
Yes.
No. In runescape, there are lots of places you can fish swordfish.
You need level 30 fishing to fish salmon.