During an HD scare with my bitch a few years ago I submerged myself in forums, books and Q and A's with vets and board surgeons when it comes to surgery options.
From what I learned, specifically with larger dogs, a TPO (Triple Pelvic Osteotomy) if your dog is eligible is the most preferred route. What makes a dog eligible? Typically the dog MUST be under a year old, reason being, nothing is actually replaced as in a THR (Total Hip Replacement). There must be little to no wear on either the acetebulum or femoral head. This surgery is for a specific "type" of hip dysplasia as there are different "kinds". Some dogs have shallow sockets (acetebulum), some are lacking angles in their femoral head. TPO's break the pelvic bone in three areas, then place the acetebulum at the desired angle so the femoral head fits inside. As with any of the HD surgeries, there is intense post-care, usually involving 6 months crate rest and extremely limited activity BUT most dogs can carry out a very active life, even competing in agility competitions after surgery.
Next most preferred surgery for large dogs again specifically is Total Hip Replacements (THR's). This is where the hip is completely replaced. This surgery is usually performed on older dogs, or dogs with significant damage already done to the joint which prevents the option of a TPO. Same recovery time as a TPO, around 6 months of crate rest and extremely limited activity. Depending on the age of the dog, recovery rate is high in those that take care post-surgery. Once again dogs can compete in sports like agility after surgery.
Last option, that I know of, is a Femoral Head Osteotomy (FHO). It's been done in the past only on smaller dogs as the femoral head is completley removed and the muscles and ligaments offer the support for the pelvis and hips that the femoral head normally would. I've read about it being done on larger dogs although the board surgeons I spoke with do not reccomend it, nor would they do it themselves. I'm not sure about the after-care of this option, nor the sucess rate as it was not an option I looked into for my large dog.
For dogs that suffer mild hip dysplasia and for owners that decide surgery is not in their best interest, keeping the dog active in low-impact activities to keep the muscles strong around the pelvis area is also extremely important. Swimming is the absolute best way to keep those muscles strong, but limit the amount of stress on the joint.
And also, something that I went through myself, treat the dog and not the x-ray.
My bitches x-rays showed that she had mild hip dysplasia at 14 months of age. My vet immediately urged me to get a TPO while she still could as there was little to no damage done to the joints. It was very "rush, rush". After speaking with a board surgeon that examined her x-rays he told me exactly that: Treat the dog and not the x-ray. If the time comes she can get a THR, but he was reluctant to believe that she would ever be affected by it, possible when she's older, in the form of "normal arthritis". My dog suffered from no symptoms, she wasn't limping, sore or slow to get up after lying down, but her x-ray said that she had hip dyplasia.
So my most important piece of advice through experience is to look at your dog and decide, not just the x-ray.