The NSS has over 200 local grottos, or clubs, with members who can give safety talks and lead trips. Most caves are on private land, ask the landowner, or managing agency for permission first. If they say 'no', leave. Never cave alone. Three sources of light, including a headlamp attached to a helmet.
Caves are more than just dark, there is no light.
No matter how long you wait, your eyes will not adjust to the dark. Wear comfortable foot gear appropriate for caving. Boots or sturdy shoes with lug type soles work well. Wear gloves and warm clothes. Bring enough food and water for an unexpected stay in the cave.