Flashing is mostly waiting around. The ten minutes that actually brick phones are the first ten, when you’re excited and skipping steps. Run this list before you type a single fastboot command.
Back up what the cloud doesn’t keep
Photos are usually fine if Google Photos was on. What walks away: SMS threads, 2FA seeds in your authenticator app, WhatsApp’s local backup, emulator saves, the note with the router password. Copy the entire internal storage to a PC before you unlock anything. Unlocking wipes the phone. Every time, on every device, no exceptions.
Move your two-factor codes to a second device first. Getting locked out of your own accounts after a wipe is a rite of passage, and it stings for days.
If the phone still boots, `adb pull /sdcard/ ./phone-backup/` copies the lot while you make tea. Least glamorous command on this list, best return on the two minutes it takes.
Charge it past 70 percent and leave it plugged in
Flashing a 2 GB system image takes eight minutes on a Pixel 6a with a good cable. The same flash on a Redmi with a tired cable takes forty, and a battery at 20 percent will not survive forty. Fastboot refuses to start at low battery on most devices. Recovery mode does not care and will happily kill the phone mid-write. `fastboot flash system` interrupted at 60 percent is how paperweights get made.
Spend $8 on the cable
Use the short thick one that shipped with the phone, or a cable printed with “data” or “USB 3”. Gas station cables charge fine and transfer nothing. You’ll know because `adb devices` returns an empty list and you spend an hour reinstalling drivers. Windows users: install the Google USB driver, then the OEM’s driver, then plug into a rear USB port on the desktop. Front panels and unpowered hubs drop connections during long transfers. macOS usually just works, which feels unfair to everyone else.
Match the file to the exact model
“Galaxy A52” covers four phones. The A52 4G, the A52 5G (a52q), the A52s: different firmware, different partitions, same name on the box. Go to Settings, About phone, Model number. Read it twice. For custom ROMs, confirm the codename first with `fastboot getvar product`, or `adb shell getprop ro.product.device` if the phone still boots. Xiaomi’s budget line alone runs through dandelion, lavender, whyred, vince, and a dozen more codenames.
Verify the download too. ROM threads post md5 or sha256 sums for a reason. A half-finished zip fails in TWRP with `Error 7`, or worse, flashes clean and bootloops the next morning. Compare the hash. It takes four seconds and saves an evening.
Read the last three pages of the thread
The first post gets written on release day. The last three pages are where owners report that the Android 13 build broke contactless payments, or that the fingerprint vendor blob vanished in v2.4. Ten minutes of reading beats an hour of reflashing. Note the file names people quote as working. Note the firmware version they say you must be on first.
Then go flash something.