Remove old hoses from barbed fittings.

[Reefmagnet]

Using water pump pliers to twist the hose off just above and at the barb works pretty good, even on ancient hoses.

[a64pilot]

Save yourself a huge amount of angst, bruising and cussing, cut them off.
I use a razor knife and cut through to the barb, it may put a little cut in the barb but that hurts nothing.
Before you cut them all off, do one or two to see what your getting into.

[sailorboy1]

I cut them off!!!! Better to do that than break the fitting or ripping up your hand.

[timeout2]

Utility knife with new blade will cut through any hose not wire reinforced.
Once slit tap a small or medium screwdriver into each side to peel hose away.
Heat gun is an alternative.

[Cheechako]

Heat gun or hair dryer with caution. But frankly I HIGHLY recommend you replace any nylon fittings. Nylon is known for suddenly just breaking after many years of service. It can be very tough for years though. But the fittings are what.. $3-4 each?