I’ve come across multiple ways of doing it but so far the best way is the following (I assume you are on i386 platform and you have access to the net):
1. Download boot.img.gz from Debian website
2. Download the net-install image choosing i386.
3. Plug your USB drive into a Linux PC, open the shell and type
$ dmesg
Last few lines should be like the following:
sd 7:0:0:0: [sdb] Attached SCSI removable disk
sd 8:0:0:0: [sdb] 4030464 512-byte logical blocks: (2.06 GB/1.92 GiB)
sd 8:0:0:0: [sdb] Write Protect is off
Now we know it has been mapped as sdb
4. Use zcat to load the boot.img.gz onto your USB drive
# zcat boot.img.gz > /dev/sdb
CAUTION!!! this will destroy the entire data on the USB drive, make sure you have done the backup.
If you get an error ensure the following:
- You are root (don’t use sudo)
- The USB drive it’s not mounted, if it is umount it before issuing the above command.
5. Now mount the USB drive and copy the net-inst.iso image on it.
All done! Now plug it into the box you want to setup and enjoy the old fashion Debian installer 
