I don't want to be a downer but... well Terrigal isn't that great a party scene. I live nearby and regularly go out in Terrigal. You'll still have a great time- during summer the clubs are busy and with lots of friends you'll be fine. But hmm.. if you're not from Sydney I'd recommend hopping on the train down to there for a night or two.
Florida Beach Bar - 'snooty' and 'upper class'. You can't be really drunk to get in here, they're pretty strict on who comes in and you have to be reasonably dressed (as in no thongs or boardies). They like to think they're heaps upper class but it's alright, just don't be blind when you show up and play sober as you show ID. They close at 2am (and in case you don't know, curfew around here is 2am so if you want to continue the party get out and get into another club before 2!). If you can't get into 'the beery' as it's called, Sirens! Free entry.
Sirens - A hot box. It's a tiny room, dance floor and bar in one. With a tiny balcony. It's always stinking hot in there. I actually generally have fun there but people whinge about it being crap. I guess just because it's so small and since the balcony is so small they limit how many can go out there and shut it off at about 12 or 1. This means you pretty much have two options for the night- dance or buy a drink and stand around drinking because it's too loud to talk. Meh. I always have fun. This is usually the only club that is open 7 days during summer. They also close around 3-4 depending on how busy they are. Usually $10 or $15 entry.
Terrigal Pub - Saturday nights is now oldies night. It never used to be, but the last few months Saturdays are just old people and it's really quiet. So Friday night is the go. That's usually fun, but at about 12 they start slowly kicking out people for no reason. It's bloody annoying! I've never been kicked out personally but you always see someone who is quietly sitting down or something be escorted out. So you can't get stupid drunk here or the chances are you'll get kicked out. They also close at about 2 so head on over to Sirens before 2 if you're not ready for the night to be over. Free entry.
Note: These three are within walking distance of eachother. So if one fails, no sweat! Walk on over to the next. Terrigal Pub is over the hill so that's not a fun walk in heels (be drunk before attempting this walk if you are a female. Or take the easy escape and go barefoot).
The Woodport Inn "Woodies": This is in Erina which is annoying because you can't walk there from any other club destinations. It's roughly a $15 cab ride from Terrigal or you can call up the courtesy bus and get there for free. They do a Wednesday night 'woodies' which usually hits capacity during summer (but they're also usually open Friday and Saturdays, at the moment they're only open for Bounce but I'm sure during summer they'll be open again Fri/Sat). It's a pretty dirty club but I suppose it's alright when it's busy. They have a large outdoor area and two dancefloors (sometimes two others open up but they're usually crap). It's usually $10-20 for entry depending on if they're having an event. But it's guaranteed it'll be at least $10 unless you get there before 10pm. Add them on Facebook and you'll be able to see their events and see when their free entry is etc... Usually closes anywhere from 3-5am.
Pulse: Lol. If you want to get ridiculously drunk with limited consequences, Pulse is the club for you! It's in Gosford, about 15-20mins from Terrigal. It's dirty and crap but it's the one club around here where you can get as drunk as you like and they don't really care. People seem to have fun when they go in large groups of people they know because it just becomes like a venue for your own party. You don't really want to meet new people at Pulse... Usually $10-15 entry, closes about 3-5 depending on how busy.
Hope that gives you a bit of a rundown! Let me know if you have any questions. Here's a little breakdown for you of what's good during summer (IMO):
Monday: lol nothing
Tuesday: lol nothing
Thursday: lol nothing
Friday: Pub/beery then Sirens
Saturday: Woodies if there's a special event but I much prefer the beery and then Sirens
Sunday: Beery for 'sunday sesh' in the afternoon/evening, then Sirens afterwards
When you're out, meet as many people as you can and make friends with fellow schoolies. There's not many schoolies but the odd few groups, so become friends so you can party on during the week when the only thing that's open is Sirens.