The absolutely best and easiest way for me was the MMC64 cartridge which can locally, from your C64, transfer D64 images from the MMC/SD card onto the 1541 and the other way around. Thank god I don't have to mess with the X1541 series of cables anymore. Having to have a dedicated PC with a compatible parallel port and preferably a real MS-DOS environment + a compatible X1541 cable was a pain.
I believe that the newly released Retro Replay cartridge is also able to perform this function.