I agree with Jake and Field's reply below Jake's.
When you change your training, or start something new, you'll always have soreness. If you are able, the best way to prevent that is to do it year round to a lesser degree. Maybe keep trail runs in your program but at a frequency of 3 to 6 times a month in your "off" season. This will be the most effective way to not get sore and keep in shape.
No supplement in the world will prevent muscle soreness...and I am a Nutritional Biochemist in the nutritional supplement manufacturing business. I could sell just about any supplement to anyone, but I won't sell something that won't work for someone or is misleading in anyway, like most fitness magazines (and their ads) do. Some will assist with recovery to some extent but the soreness will still be there.
As mentioned here, diet certainly helps. I tell clients in a simple way the best way to eat...plants and animals in their most natural state. Of course, I go into more detail than that. But, you get the idea. Heavy skinned berries (like blueberries) are great and should be a staple for their nutrient density. Calorie for calorie, it is hard to beat the nutritional value of blueberries. Fish or fish oil is a must in our diet. Consistency is key...you can't eat right 2 days in a row and then not for a week.
Topical creams that reduce pain and inflammation will probably offer the best, quickest relief. Find a strong one with emu oil, a blend of herbs/spices that reduce inflammation and delivery system that allow it to penetrate the skin into the underlying tissue. The popular one's at the pharmacy that cost around $5 will not work...just make you smell. Don't get me wrong, you need high amounts of camphor and menthol for it to be effective but that's all they have for active ingredients and that won't work.
Good luck!