Terraria guide: How to survive the solar eclipse (for the first time)

At this point the Wall of Flesh is killed and your world is in hardmode after preparing for the spread of the corruption/crimson.

And then... the solar eclipse. How bad could it be? ... Just hide in your house (and avoid the reapers!) and NOT the first floor. The reapers won't be able to reach you if you are not on the first floor. Same goes for the NPCs unless you want them to die. They are just upgraded wraiths. Not fun. Hopefully by the time this has happened you are better equipped (or you summoned the solar eclipse with the solar tablet after killing Golem). If it randomly happened and you are unprepared, that is a problem. The campfire + heart lantern combo will help with your life regen a lot. Any warding accessories will greatly help too. 

How to prevent monsters from entering your shelter (except those stupid reapers)? A 2x2 hole directly next to the door will stop them from opening it. (they will jump but can't open the door). Or use an actuator wall for a door with a switch. Either one will do. 

For resources, go after creatures of the deep and vampires. Those have a rare drop which are great accessories. Creatures of the deep drop Neptune's shell which turns you into a merfolk underwater. Vampires drop the night stone. Combine the Neptune's shell with the celestial stone (rare drop from werewolves which spawn on a night with the full moon) to get the moon shell. Do the same but with the night stone and the day stone (A drop from Golem). Take the celestial stone and combine it with the moon shell to get a celestial shell (which combines all 4). All of this is done at the Tinkerer's workshop. Do note that the celestial stone is useful for summoners. Though the celestial shell is useful across the board. 

This is the main reason to bother with the solar eclipse honestly. The celestial shell is well worth the effort to get. 

The other item worth getting is the broken hero sword. This is a drop from Mothron (PC). It spawns after all the mechanical bosses have been killed (Twins, prime, destroyer). If left alive long enough, it will lay eggs that if not killed spawn baby Mothrons (not fun). Mothron is rather easy to destroy with good ranged weapons (magic, bullets, arrows, whatever). Though it does go through walls... yea your house is not saving you from this one. Thankfully Mothron does not constantly spawn (it spawns infrequently and you can't miss it unless you afk or something). 

The broken hero sword is used to craft True Night's Edge and True Excalibur. Combine Night's Edge/Excalibur with a broken hero sword to get the True variant. Two are needed (PC) to make the Terra blade. Then take those and combined them to make the Terra blade. Craft these at the mythirl/orichalcum anvil (Depending on what your world has). 

Any weapon that attacks though walls (solar eruption for example) will help a lot. The only flying monsters are vampires and Mothron. Note that the possessed can climb walls.