Volume
Decent exercises.
Don't forget front squats too.
Deadlifts (back & hamstrings)
Smith squats (strangely) good for going ATG as you can get massive ROM and there's minimal/no load on your core.
Also stance is another one, which is the smith is good as you can put your feet/heels together and really smash lateral quad & glutes.
Again on the press vary your stance. Sometimes feet up high, far apart, close together, down low (not too low though). Make sure you're coming nice and deep on the press too.
Slow negatives as well are good too. Controlled extensions.
I started off with a chap I met in the uni gym. Just crunching out sets of 20 reps on the press. When I first began after 3 sets of 75KG I was spent. Learnt to push through barriers and quite literally ignore the pain! Used to finish with barbell lunge walk, pritty punishing!
In terms of routine I think I mostly favoured ascending pyramids (increasing weight and decreasing reps). And then depending on how I felt drop setting and burning out on a descending pyramid.
I think my most memorable was back squats:
60 x 25
80 x 10
100 x 10
110 x 8
120 x 6
130 x 4
140 x 2
150 x 2
100 x 26
70 x 31
Then onto press, hamstring curls (too smashed for SLDL!) calves and then FST-7 for extensions.
You're legs are massive muscles with insane amounts of endurance so can really take a beating, providing you can take the DOMS! FF measures his leg workouts in volume so however many tonnes you've press/extended/squatted. Obviously 100KG x 10 reps = 1 tonne

My current workout (have a pants comercial leg press as opposed to plate loaded so the physics are slightly different) but i'll see about 15-16 tonnes of volume on press alone in 20 minutes flat or less with 60 second rest periods and 10 sets.
Currently working on a sort of modified GVT programme. I had been squatting before that but found myself a bit bored of it and really wanting to isolate my quads so have opted for the press for the duration of this programme. 4 second negatives with a weight I can get around 10 reps with for the first 3 sets and then gradually start to fail earlier and earlier on the remaining 7 sets. Then some extensions 4-5 sets just getting as much time under tension as possible.
Hamstrings get hit with my back day at the moment. All about the range of motion and time under tension! I'm sure others can share some good advice with you too! Took me around 2 years to slap on about 2" to each quad and get a decent squat weight. So be patient but it's quite rewarding. Benefits it'll give you're upper body and other lifts are immense.