I don't have too much specific feedback, but I know one thing that has irked me in the past (and irked users of services I've worked on) is when the OAuth permissions requested are very broad. For example, why request "write" access to a resource if you don't need it? In other words, ask for the bare minimum permissions from the user that your app may require to function.
What stack are you developing in? Maybe there's a solution like https://github.com/intridea/omniauth available that you could utilize if applicable.
What stack are you developing in? Maybe there's a solution like https://github.com/intridea/omniauth available that you could utilize if applicable.
Hope that's helpful and good luck :)