Linux
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1. To get help on the command, either
# useradd
# man useradd
2. To use default preferences in /etc/default/useradd
# useradd <username>
# passwd <username>
Solaris 9
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1. # useradd -d /export/home/newuser -m newuser
-d => home directory
-m => create if the directory does not exist
or
2. # useradd -d /export/home/user1 -m -g other newuser
-g => group "other"
or
3. # useradd -d /export/home/user1 -m -g other -u 1050 newuser
-g => group "other"
-u => uid "1050"
then, set the password
4. # passwd newuser