I exercise 5 times a week. 30 min on elliptical and 20-25 minutes lifting weights. I do 4 reps of each station on my weight machine (2 leg exercises, 4 various arm exercises).
It has really helped my bat wings but I have FAT thighs and would like to build some muscle in them but do not know the best way go do it. Should I be using heavier weights with the leg exercises? instead of doing the 4 reps of 10 using lighter weights?
What other type of exercises can I do to help build leg muscles?
I am getting close to my personal goal and the next goal I would like to work on is really building some muscle and getting some definition in my arms and legs.
I want to go from flabby to buff.

A couple thoughts:

* I do think that you should do higher weights, and smaller numbers of reps, if your goal is to build and strengthen your muscles. I aim for the weight that I can do 6-8 reps/set, for 2 sets. When I find I can do 10 reps easily, it's time to up the weight.

* If you are lifting that way, don't do it every day - let your muscles heal and repair for a day in between lifting workouts. That's what allows them to build. Some people do lower body lifting one day, upper body lifting the next day, repeat. I do a full-body lifting workout every other day. I do a shorter cardio workout on lifting days - really just a warmup, 15 minutes or so - and a longer more focused cardio workout on non-lifting days.

* Don't be limited to your machines - add squats, lunges, and lateral lunges to your workout. These are the best exercise for your legs, butt, and core. They are great for building functional strength and balance too. You might be surprised at how difficult they are to do, especially the lunges, if you have mostly been lifting on machines. For your core and your arms, you can add pushups and tricep dips (on a chair or bench) - also, surprisingly hard to do. I always thought of myself as strong and did a lot of machine lifting, but it took me a long, long time to be able to do real pushups.

Have fun

Squats, deadlifts, lunges.

Start with body weight and then add weight as you go. 3x10 is fine, but you should be using a weight that makes finishing those sets a real challenge (but not impossible).

And Carter is right--you need a rest day in between lifting with the same muscle groups.

You need to do body weight resistance exercises. Do squats and lunges and you will see results. You can look up youtube videos for proper form and their are lots of variations so that you don't get bored - eg. walking lunges, reverse lunges, plie squats, wall squats with an exercise ball. I will be honest - they feel pretty awful when you first start but if you keep it up then you will see results.

The best result I noticed after I had been doing them for a few months was that when I got on my bike I could ride up hills that I never would have been able to get up before. That was an awesome feeling.

Great advice. Will definitely see if I can figure out how to use UTube to look up proper form on the squats and lunges. I will add them to my work out.
What is using body weight???
Thanks so much!

Using body weight just means doing exercises where the resistance comes from the weight of your own body. You don't always have to pick up heavy objects in order to give your muscles something to do - just squatting or lunging requires your legs and core to support and move a significant amount of weight - the weight of you! Same for pushups - what makes them hard isn't that you have some barbell on your back, it's that you are trying to move the weight of your body - hence, "body weight exercises".

As you get more comfortable with these exercises (and they start to get easier as you simultaneously get stronger and lose weight) you may want to pick up something heavy while you do them. But at first you probably won't have to.

And don't forget deadlifts--for your glutes. You could start with romanian deadlifts if you wanted, and work up to proper deadlifts.

You've gotten some great advice so far. I agree with all of it- lunges, squats, etc.

Regarding number of reps and how heavy a weight, the last rep you do you should almost not be able to do it. In other words, you should physically not be able to do another rep. Don't strain your muscles or injure yourself, just push your body to the limit. Lifting until you "feel" it or until you get tired doesn't usually deliver the results you want. The last rep should be almost impossible!