QlikView is very flexible in the naming conventions you can use to keep the script maintainable within an organization. See for example the response of Sokkorn on what pre- and postfixes you can agree upon within your organization.
There are some special characters to take into account. The most important are:
// indicates a comment line
/* A LOT OF TEXT */ indicates multiple lines of comment between the slashes
$ indicates a variable is to be used
In the script you will see change the color if something special is taking place. For example blue indicates a function, gray is a variable and green is comment by default. And all commands are ended by a semicolon (;)
If you need more details I suggest to check the help file for qlikview, follow some training and/or google for it as there is much already available (and in detail).
As far as I know this character has no special meaning. It is sometimes used in functions like num# and date# which actually tell QlikView how to transform the value between brackets into a number or date. In comparison the version without # (num and date) only tell QlikView how to display the number or date.