You have to get an invite to fashion week.
Just like private trunk sales and any events regarding and the exclusive couture crowd you have to be a major buyer of a line to get invited if you are not professionally associated with the industry.
Runway events are usually reserved for influential figures and press surrounding the industry. It is not a gawking event.
The things you can do at fashion week in Paris are going outside of the 'déflié' and sometimes you can see the stars and if you know something about fashion you can spot the important figures that finance, inspire or create the lines. For example all of the heads of LVMH usually go to all of the DIOR and other marks incorporated into the luxury group's shows.
Sometimes you can get into parties but those again are serious long lists for reserved clients, aficionados of the lines, models and celebrities.
An alternative: go out and party in Paris and you will surely have fashion TV playing in the most glamourous of bars and clubs. That way you can watch that day's runway shows, drink, and have a great time on your own.
For more information on Paris, must-sees, and insider info checkout my blog:
http://emilieinparis.wordpress.com