basic samba config in debian

apt-get install samba

groupadd guest

Make sure the new user has no system logon if you do not want them to get into you system via e.g. ssh.

#guest user
useradd -g guest -s /sbin/nologin 
smbpasswd -a 

Edit the smb.conf with appropriate values having the filesystem on disk already prepared.

# vim /etc/samba/smb.conf

[global]
...
   invalid users = root, guest, gast
   write list = @admingroup
   hosts deny = 10.99.0.0/255.255.0.0
   guest ok = no
...
#disable cups error logs
printcap name = /etc/printcap
...
#######################################################################
## shares
#######################################################################

#######################################################################
[sharename]
#######################################################################

#tell user what this is
comment = whatever you like to
#location on disk (softlink)
path = /path/to/share
#custom volume name
volume = sharename
#let user browse dir
browsable = yes
#write access - public no
writable = no
#we hate guests
guest ok = no
#who is valid
valid users = @admingroup,@guest
#set write only to admin group
write list = @admingroup
#look and feel
directory mask = 0775
#adding files
create mask = 0775

For an upload dir, set filesystem mode to 777 and then adapt the following:

writable = yes
write list = @guest
directory mask = 0777
create mask = 0777