Get Big, Masculine Legs

To have masculine legs, you don't always have to resort to bodybuilding. But here are a few ideas, but these are in no particular order.

Steps

Walk everyday. This slowly builds up a large amount of muscle in your legs and helps strengthen bones prior to a "real" workout.
Sprint, don't jog. Sprinting exercises, especially sprinting uphill and plyometrics, can build up your quad strength.
Leg Press Machine. The leg press machine is a standard machine of choice when you want to do weight training in the gym.
Calf Raises A simpler exercise for resistance exercise for your calves using your own weight.
Squats are a very good way of building leg muscles if done correctly, and a good quad workout. For advanced lifters, you can add a calf raise at the end of the lift.
Dead Lifts a great overall body exercise, and especially works glutes, hamstrings, and quads. This exercise, when done correctly, releases the greatest amount of human growth hormone (needed for muscle development) of any exercise out there. Should only be attempted if you know what you're doing though as it is prone to injure rookies.
Also lunges and exercises like jump squats can really help to develop leg muscles if they are performed properly. It is recommended that you see a physician before starting any exercise routine.
Attend sports such as soccer. The sport really focuses on your legs.

Make sure you have spotters when you do leg presses. A wrong technique can damage your knees. On squats, the closer you can get your elbows parallel to the bar the straighter your back will get, letting you get under the weight a whole lot better.

Never attempt any weight-related exercise if you 1) Don't know what you're doing 2) Think you know what you're doing but haven't done it before 3) Don't have someone to show you the proper techniques.
At the bottom of the lift on squats, if you feel that there is no way you can come up with the weight, simply open your hand and let it roll to the top of your fingers while stepping out from under it
Be careful not to strain or sprain any muscles.