Butts and thighs, no matter your gender, are some of the most difficult areas to train. Both areas require pretty much constant training to maintain and improve what your mama gave ya! They are some of the most frequently used muscles in a person's every day life and it is quite important to keep these guys engaged and ready to fire at any time.
The 10-20-30-40 sequence is meant to be repeated 5 times. If you can do more, awesome, do it! You want to feel a burn, that is when change happens. After each round, give yourself 60 seconds rest.
10 jump squats: These can be regular (non jumping) squats if you have injuries that don't allow for the full exercise. Step one: Stand with feet hip distance apart and bend knees to 90 degrees. Your weight should be in your heels at this point--you do not want your heels to come off the ground until the jump part. Step two: Propel yourself into the air leading with the balls of your feet. Step 3: Land softly and head right back down into the next squat.
20 Sumo (wide leg) squats: Stand with your feet wider than hip distance (how much wider will vary from person to person) with feet pointed out at 45 degree angles. Lower your body, leading with your butt and bending your knees to 90 degrees. Return to standing and repeat.
30 Lunges: These can either be done one leg at a time staying in the same space (static) or as walking lunges (dynamic). However you decide to do them, make sure you can always see your toes in front of your knee. When you allow your knee to extend beyond your toes, injury happens. Repeat 30 lunges with each leg forward. If you're doing walking lunges, do 60.
40 Donkey kicks with each leg: These may feel stupid, but they work wonders on the arse. Step 1: Get down on all fours with a neutral spine. Step 2: Bend your knee in towards your chest. Step 3: extend the same leg (keeping knee bent and foot flat as if it's holding a tray) up towards the sky. Repeat.