My right leg has always been slightly larger and more muscular than my left. I have lately been trying to address this. One thing I found was that even though performing movements with two legs at a time, I was leading with my right leg without realising it - i.e. my right leg was taking more of the weight and thus doing more of the work. So what I have to do is focus on my left leg throughout the movement - even to the extent where I would lift as much of the weight as possible with the left leg and try and keep the right one out of it completely apart from actually moving it - although you won't achieve this.
Obviously you could also try unilateral movements so you can give the smaller leg more isolation.
Also, check you from on squats and see if as you come up you are off centre - many guys do this and it is hard to rectify - so really concentrate on squatting technique and don't be to concerned about weight until you have nailed it. Look at simple but often overlooked things like ensuring you are face on to the mirror - look at the bar as it sits on your traps before you squat - is one side further forward than the other - causing the bar to be at an angle. Watch your form in the mirror as you come up - is you torso slightly over to one side rather than dead centre? Look at all these factors.
Another thing is that you probably lead with your bigger leg in everyday activities - climbing the stairs for example - so change it round.
