A wetsuit should fit snugly but not overly tight. The key to a properly fitting wetsuit is to balance between flexibility and insulation. Here are some guidelines to help you ensure a proper fit:

Tightness: The wetsuit should fit tightly against your body without being excessively restrictive.
There should be minimal gaps or folds in the material, especially in areas like the armpits, crotch, and behind the knees.
A snug fit helps to trap a thin layer of water between the suit and your skin, which then warms up and provides insulation.

Length: The wetsuit sleeves and legs should reach your wrists and ankles respectively, without any excessive bunching.
The suit should cover your torso completely, with the neckline snug against your neck but not too tight.

Flexibility: You should be able to move your limbs freely without feeling restricted.
Check the range of motion in your shoulders, arms, and legs to ensure the wetsuit allows for comfortable and natural movement.

Neck Seal: The neck seal should be snug but not constricting. It should prevent excessive water from entering the suit.
Some wetsuits have adjustable neck closures to achieve a comfortable fit.

Zipper: If your wetsuit has a zipper, it should close easily and securely. A back zipper or front zipper may be used depending on the wetsuit design.
The zipper should have a pull cord or strap for easy opening and closing.
Remember that wetsuits may stretch a bit with use, so they might feel slightly tighter initially.