Liability waivers are a good idea when inviting people to come on your property. Give them the waiver in advance of the activity; this gives them time to read and consider the waiver before signing it. This gives you a stronger legal standing with regards to the waiver.
The most important part of reducing your liability is exercise prudence in your business – enforce safety rules. Also, take common sense steps to reduce the chance of someone injuring themselves on your property. Check deer stands before hunting season. Make people aware of any places they need to avoid on your property. These steps can help to reduce your legal liability and keep your customers safe.
Check out the video of Mike Massey of Outdoor Lawyer discussing liability waivers.