Do use heading cuts to spur growth in the right direction. Unlike thinning cuts, which remove a branch, heading cuts shorten a branch down to a bud you want to encourage to branch out. Though it seems counterintuitive, you need to prune the shorter side of a lopsided shrub to stimulate growth and even it out. Position the pruner on the part of the stem you want to remove, just above a bud that will grow in the direction you want to encourage.
Don't remove more than one-quarter of a stem's overall length in any single cut. For shrubs that are dramatically lopsided, use thinning cuts to remove older wood from the longer side as well as heading cuts on the shorter side.