
Fortify the gate: Quickly and carefully enclose the gate (cobblestone is great for this). Use the first 10 obsidian to build a nether portal (economical version), activate it, step through (cautiously) and hold your. (Plug the coordinates in one at a time -or- as a comma separated list like: 100,66,300. (I keep a browser open to alt-tab between the game.) (See the F3+I Parser tooltip for possible short-cut.) At the spot you want your gate/return portal hit F3 and find your XYZ coordinates. Collect 20 obsidian blocks and create a. I tend to do this even in worlds where I'm alone, so I can find my gates when I'm mapping overworld places to my nether-highway (. Then I check my XYZ to see if I need to explore to different XYZ to build my own return portal. When I step through to the nether, if the gate is new, I build a quick enclosure around it to avoid getting attacked or burned up by What I learned to do was find my XYZ coordinates while building my gate and carry cobblestone, 10 obsidian, and flint with me to build a return gate (if needed).
So, while panicking, I scrambled around trying to avoid phantoms and angry mob babies, then fell into a chasm while trying to find my gate again! Ok fine, but when I stepped back through, it was in a "room" that had been blown up by a creeper, it was dark, and I didn't recognize anything. Once, I built a portal from my home at XYZ and stepped through to appear in someone else's gate room. If you play in a world with others who use the nether, it's not uncommon to appear in an unexpected place when stepping through a portal.
One trick though: You might need to pair your gates. The scale of the nether makes each step ~8 steps in the overworld.
Minecraft is fun! (Duh!) When you delve into the nether you might consider using it for "fast travel" in the overworld.