dd too but it may not be the recommended approach for newbies.
dd, backing up to a removable drive, I recommend always to check what drives exist before connecting the destination drive e.g.
ls -l /dev/sd* and then connect the destination drive, then check the drives again. So you are really really sure that you are going to use the correct destination drive.
I also recommend using
fdisk -l /dev/xxx where
xxx is the name of the device, as a sanity check on the size of the drives that you are proposing to use. Again, this can help to make sure that you have source drive and destination drive the correct way round, and may also highlight if something is about to go wrong (i.e. destination drive is the correct device but is smaller than source drive).
One disadvantage of
dd is that it backs up the entire source drive, no matter how full or empty the source drive. So if the source drive is mostly empty then you waste time. (However the upside of this is that it always takes about the same amount of time to do the backup, so you know what you can achieve while waiting e.g. how many coffees.)
One advantage of
dd is that it works regardless of partitions and file system, even encryption. You just get an exact image, which should work to backup just about anything e.g. even a Windows drive, or a file system that is not even recognised by (your version/distro of) Linux.
Another disadvantage of
dd is that the UUID of the destination drive ends up being identical to the UUID of the source drive. This is of course what you want and is fine as far as doing the backup and fine if you ever had to restore the entire disk BUT means that the destination drive doesn’t automatically mount and so is not as convenient if doing a selective restore (just one file or a few files or one directory tree or a few directory trees). I don’t know whether this behaviour differs between distros/versions.
Really there should be a support article / FAQ / something about backing up - since everyone should always have a backup strategy.