I want to create a fictional language for my fantasy world, but I'm not sure where to start. Can you give me some pointers, or do you know of a resource that could help me get started?

I want to create a fictional language for my fantasy world, but I'm not sure where to start. I remember reading something about Tolkien's Elvish dialects, but I don't want to just copy them and I'd love to know where to start from scratch. I've tried talking to my friends who are studying language at college, but they're not sure where to start either. I've also looked it up on Google, but I'm not sure which of the resources are going to be trustworthy and reliable. Thanks for your help.