A petition, whether on paper or online, is a tool with particular uses.
You need to know what you want to accomplish before you decide if a petition is the right tool or not.
If you want to influence the passage or failure of a particular bill or piece of legislation, a petition is not the right tool. Rather, you should focus your efforts on visiting with your elected officials. Using a petition for this goal is waste of time and effort.
Bonus tips: if you organize a petition, aim it at the people who can do something about the problem. For example, don’t petition the White House if your concern is at the state legislative level. Also, if you are not a constituent, the impact of your petition will probably be reduced.