How to survive hell
Before you enter hell make sure you have an obsidian skull - This will allow you to stand on Hellstone blocks and hellstone.
Make sure you have alot of dirt.
Make sure you have health potions.
When you enter hell surround yourself with dirt this will be a good starting point.
Dig in any direction you want. Please be wary that Bone serpents will attempt to attack you so expanding the size of your dirt room.
Lava Slmes - Annoying as hell try not to kill them if you can help it as they will make your life harder if you kill them. (1 block worth of lava)
Demons/Voodoo demons - Uses circular scythe attacks make sure you are surrounded by a surface preventing there attacks from entering. They can go through Wooden platforms.
Hellbats - Usually in swarms, mainly pests and do alot of damage. So try to stay away.
Bone Serpents - Easy to locate and kill as long as you have a weapon that does atleast 10-20 damage per hit.
Imps - Teleporting monsters that only teleport in spaces with 3 room or higher so minimize chances. There attacks can go through walls. Recommended to take out with vilethorn.
Digging under the hellforges can also pick them up.
Also Ashes replace the dirt layer (These are more of a pain than a useful resource. Theres a 1 in 6 chance that the ashes fall on you if you mine anything around it. So add dirt underneath the layer of ashes to prevent from falling.
You can also replace the lava with dirt so it removes any unwanted lava.