How can I tell if a BJJ class is a good class

I'm from Scotland and there's a major shortage of BJJ classes, like 1 per city. The only belt I have is the one I use to hold up my jeans, I'm a complete beginner, but I want to make sure I'm putting my money in the right place. So is there anything to look out for to check if my class is a good class or not?

If anybody has input it would be greatly appreciated :).