linux:
mount -t smbfs //hostname/sharename$ /mnt/mountpoint -o username=username
you are then prompted for password.
Just use whatever you usually log in with.
on windows
start, run
\\linuxmachinename\sambasharename
username:
linuxmachinename\accountname
then password.
you can specify hostname then \ then username (i.e linuxmachinename\accountname as above) to ensure that machine's useraccounts are used.
Always turn off any zone alarm or anything when trying to test (except for external connections, of course.)