You could try a head collar or harness as an interim measure (a choke collar on a pulling dog is just going to result in physical damage - possibly irreversible - to the dog).
You need to be aware that devices like that are only crutches though. They do NOT teach dogs not to pull, all they do is limit the animal's ability to pull with quite as much force. Take away the crutch and you're back to square one. The long term answer is actually training
One thing you might consider - every single step forward you take when a dog is pulling on a leash is reinforcing and rewarding the pulling. In any other terms, training the dog TO pull. If you currently do that - that is, comply and move forward when the dog pulls - I'd suggest stopping.

There are plenty of threads on the forums about how to train loose leash walking that you'd find with a quick search.