Safe mode to insert data in Database?

[web_master]

Hi what is the safe(est) mode to insert data (exmple email address) into database?

 

Example:

 

$query_return = mysql_query("INSERT INTO e_group (e_group_email) VALUES ('".$_POST['e_group_email]");				
	if(!$query_return) {
		echo mysql_error();
		exit;
	}

 

I heard about a slash (/) to put is somewhere when I want to email dont be a cached on the fly between a post and inserted into dbase  - I think its good for a password too.

 

thanx