Well - at 18 I don't think you can get into bars to be honest

HOwever since you asked...
Columbia Street Tap Room and Grill, Covington, Louisiana The Tap Room is v. popular and has great music. There are several great dive bars also - The Red Barn Pub in Mandeville, The Pub in Covington, etc.
Rip's (resteraunt) in Mandeville is on the lake and is beautiful. Honestly there are so many nice resteraunts I would be doing you a disservice by listing bc i would surely leave one out... Etoile, Juniper -
Fine dining Creole restaurant with catering - Mandeville, LA,
Welcome to .:: Nuvolari's ::., you will figure it out.
Every other FRI night (I think that's right) in Covington are block parties downtown, featuring live music, food and drinks, the shops are open... They also have an "evening stroll" once a month where all the galleries are open, serving drinks, etc.
Welcome to Covington, Louisiana - there is an event calendar.
There is also one in Mandeville once a month at the "Trace" - where the bike trail starts.
The trace:
Tammany Trace - Rails to Trail - Louisiana
This is a brewery (I think the last one in Louisiana!) that has great food, offers tours, etc.
Abita Brew Pub
NO will provide so many things to do I don't think I can go into all of it! check out nola.com!
I can't say that I know of any 'clubs', but once you get on the southshore, you will.
There are more outdoor festivals and parties here than I have ever encountered. When you grab a paper you will be shocked at how quickly a weekend can fill up! And - as far as a culture shock - everyone drinks, all the time. I respectfully see that you are under 21, but wanted to let you know that it seems to be part of the gig down here... hence the drive-thru daquiri bar (God love them).