You don't have to worry about balancing the barbell.

Exactly why it can make the imbalance worse.

Since you can just push more with the dominant leg. A free barbell at least forces your to balance the bar so that both legs works nearly the same effort.

This is what I would do:

unilateral training.
Single leg romanina deadlift, King deadlift (single leg DL), Bulgarian splits squat, pistols, lunges, etc.

Or I might want to have a friend to spot me. In the event that my hips/knees/whatever senget to one side, then he has to tell me immediately. I either try to correct it while on the rep, or I reset and do another lighter rep and groove in the proper movement.

And he can also guide my movement by placing lightly his hands on my knees/hips (or both hands on the side of the knees/hips). Then my job is to follow his guide. Repeat to groove in the movement.

I may also start from low weight to, then add more weight until my form breaks down. Then practise, practise & practise using the most weight without cacat form.

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Added on October 19, 2009, 11:35 amOh, forgot to add:
I might stretch everywhere from the hips down. Hip flexor, glute, hamstrings, calves, leg swings, etc.

And also do some glute activation stuff.
fire hydrant, bird-dog, super dog.

Not sure if it's related, but I just know that stretching & glute activation are important and I would do it for the heck of it anyway.

Try simulator before go real. Smith machine act like simulator.