Note that if you use ISP to upload a sketch it overwrites the Serial bootloader. To do a Serial upload you need to re-burn the bootloader.
Be sure to use an 8 MHz bootloader or the baud rate will be wrong.
If you don't have the auto-reset circuit, you may have to manually reset the board at the right time to Serial-upload a second time. The first time should work even without auto-reset since the bootloader has nothing better to do than wait for an upload.