Skin type
Different types of moisturisers work better on different skin types. Work out what type of skin you have and then compare suitable products.
You can also shop for products designed to address specific issues, such as wrinkles. However, remember to take the marketing claims on the packaging with a grain of salt.
It's also worth pointing out that some products may have multiple uses. Retinol, for example, is a common ingredient in anti-ageing moisturisers, but it's also useful for treating acne.