If someone has Snapchat Plus, they'll have a star icon next to their name, which is a pretty subtle indicator that they're a subscriber. This star badge is usually visible when you view their profile or in chat, so you can easily spot it. Additionally, Snapchat Plus users also get a few other perks, like being able to change their Snapchat icon and see who's rewatched their stories, but the star badge is the main visual giveaway that they're paying for the service. It's a pretty neat way to distinguish themselves from regular users.
