How to protect against lava?

Lava Charm - 7 seconds of lava immunity when this accessory is equipped, found in chests in the cavern layer.

• By extension, Lava Waders, crafted from a Lava Charm and a Obsidian Water Walking Boots allows the wearer to walk on lava and also to submerge himself on Lava for 7 seconds, cumulative with another Lava Charm.

Obsidian Skin Potion - Grants 4 minutes of lava immunity, can be crafted at a placed bottle, with Bottled Water, Fireblossom, Waterleaf and Obsidian.

Fill - A player can either fill a lava lake with some sort of gravity-enabled material (e.g, Sand, Silt, Slush) or at the very least cover the top of the lake with any sort of material, as to avoid falling on the lake.

Redirect - You can create sized reservoirs near the lava source that allow control over where the lava is. You can either use gravity (in which case the chamber should be below or at the side of the source, connected by a pipe of sorts) or a system of pumps.

Reach - Since hellstone releases 1/2 a tile of lava when mined in The Underworld, digging from the other side of some block barriers allows for the ore to fall down and to be pulled to you through the blocks, up to 3 blocks away (two tile less than the maximum reach of the Nightmare Pickaxe).

Evasion - You can use Rocket Boots to fly over the lava or Grappling Hooks to sling yourself to a roof or the other side of the lava lake.

Water - If you can keep water in the area around you the new lava will become obsidian right away, before it can burn you. Of course to do this enough to get a reasonable amount of ore you will need either water draining in from above or the Bottomless Water Bucket. Water evaporates quickly in the underworld.

Buckets are stackable to 99 units, which means a single stack can almost remove a 10x10 space of lava. You can then place the lava somewhere else. A bucket can be crafted at an iron/lead anvil for 3 iron/lead bars.