What is the best greeting for a retail store?

I'm curious, what's the ideal greeting to use when welcoming customers into a retail store? Should it be formal and polite, or should it be more casual and conversational? Is there a specific phrase or tone that has been proven to be the most effective in creating a welcoming and inviting atmosphere? And does the greeting vary depending on the type of store or the target audience? I'd love to hear your thoughts on this!