
When they are on their own, do you walk them on both sides? I find with my two that they tend to stick to the side they are usually on - for Opi, the right, and Remy, the left side. When I leave the house with opi, she will actually lag behind me up the driveway until she can get on the right side.
It ahs taken a while, but I've found if you're calm and patient with them, they will get the hang of it - whenever my two try to cross my path or pull, I stop, say "no" low and calmly, then "back" - if they don't move back into position themselves, I guide them back gently. I do this every single time they try to cross or move out of position - any one time they get away with it, my training gets et back a few walks' worth!
Keep at it, they will get the idea eventually :) it's taken almost 2 years with my two, and many, many individual walks and it's just now starting to click. But they are extremely independant dogs, so I kind of expect to have difficulty bringing them round to my views on how a walk should be :D But the patience does pay off - now I can walk both dogs to a field nicely at heel on their chosen sides, then round that field on 6ft leads with them right at the end of said leads, wherever they want to be, without them pulling. Remy will try to pull if there's a rabbit or a dog, but a calm "no" and bringing him back a little (or waiting till he comes back toward me, if he's just pulling for no reason) does the trick.