Finish the gateway
A ruined portal may provide part of an obsidian frame, but it is incomplete. Inspect the frame and replace missing material before trying to activate it. Do not assume every dark portal-looking block is a usable frame block. Keep spare activation equipment available for the journey.
Protect the return route
Record the portal location, carry food and building blocks, and secure the area around your arrival point before exploring. Put an expendable buffer between your character and a lava drop. Leave valuables that are not needed for the trip at your Overworld base.
Do not carry Overworld assumptions across
A normal bed is not a safe Nether respawn tool. Respawn anchors are a separate mechanic with charging requirements; learn that system before depending on one. Ancient-debris mining adds more risks, and its tools and escape route should be prepared separately from a first visit.