OK, so you've done a scan and gotten some results. How do those help with troubleshooting. Here we discuss various scenarios and what they imply.
Correct Addresses Show Up
In general, you should be all good. There's nothing more to be done with an I2C scan. Go ahead and start trying to use the device, preferably using an example from the devices library.
If you get additional errors when trying to run the library example, post in the Adafruit forums with details.
Incorrect Addresses Show Up
Weird, but can happen in rare cases. Double check the device and make sure it is what you think it is. Some devices can have more than one I2C address, typically settable somehow by the users. Check if the incorrect address is one of these alternate addresses.
If everything seems correct but you are still getting an incorrect address, post in the Adafruit forums with details.
No Addresses Show Up
Try just scanning again. Some devices can be weird and not show up on first scan. If that still does not work, then: Check your wiring and/or your soldering. This accounts for the vast majority of issues.
Wiring
Wiring issues can be incorrect pins or even just bad wires. Double and triple check you are using the correct pins. If you are using a breadboard, try moving to a different location. Breadboards can wear out with time. Also try totally different wires. The pre-crimped prototype wires commonly used can also wear out over time.
Soldering
This is unfortunately a very common issue for beginners. Soldering is not super tough, but does take a little getting used to. There's a good general guide on soldering as well as a guide specific to the commonly used headers pins.
This photo from the first guide is an excellent summary of common soldering issues:
If you've checked all this and are still not getting the expected results, post in the Adafruit forums with details. Photos are very helpful when doing so.
