Any liability release form needs to state that the participant acknolwedges that hiking is a potentially dangerous activity and that the participant assumes the normal or common risks that come from hiking and agrees to not sue over or for them. You can't protect yourself from lawsuits if you do something wrong--e.g. if you end up knocking someone down a cliff somehow--but you can protect yourself from the normal risks (turned ankle; slipping and falling; poison ivy/oak; wildlife attack) that are alway present while hiking as long as you get the participant to acknowledge (and sign, confirming acknowledgment) those risks.