1) I hate when people say get new boots. I just bought new boots last season (Full Tilts) and still get shingbang, albeit not nearly as bad as before. Not everyone can afford new boots every few seasons, so for people like me buying new boots is definitely not happening.
2) Don't land backseat. This is the worst advice. How can you not land backseat, especially when trying new tricks? Whenever I spin and land forward, especially when trying something new, I'm prone to landing backseat. This always kills my shins, so I try to avoid spins where I land forwards. By doing so, I am limiting my ability to learn new tricks and push myself, which is the whole purpose of skiing park. Unless you don't want to learn new tricks, then be cautious when skiing and don't do anything new that may put you backseat.
So my advice:
I've tried cutting foam to put in front of my shins, custom footbeds, booster straps, ice, every remedy and even new boots last season and I still get it. I'm tall and have fairly skinny legs, so I think no matter what boot I have, there will be space between my shins. I'm also wondering if because of my height, if normal boots go lower up on my legs, thus causing like a "hinge" that adds to shin pain if that makes sense.
This summer I worked in a river all day, and biked as much as possible, which definitely strengthened my legs and added (some) muscle. I've been skiing twice so far this season and did not notice any shinbang and felt that my boots were tighter. Not much you can do now for that, but think about it in the off season. I also unbuckle my boots every time I get on the lift. I always found that when I left them tight on the lift, my shins would be throbbing at the top. Just unbuckle them, and leave them in place, and it allows your feet to get some circulation and relax. This helps me make it through an entire day of skiing. And make sure to keep your boots tight! Loosening your straps feels nice for the first few runs but then after a awhile of your legs moving around more and slamming the tongues, you get more shinbang! If you have Ful Tilts (i.e. Booters) maybe look into getting a stiffer tongue. I'm about 175 pounds and had the #4 tongue last season and got the bang. This season I switched to a #6 and so far, it seems to help me ski more aggressively.
And remember ice is your friend after skiing and pop some tylenol before and after skiing. Hope that helps!