Issues are maintained in the Apache JIRA by default, so before posting pull requests, please have a look there if an associated issue with your problem/feature/... exists already. If not, it's generally OK to directly create pull requests IF code is already available, but please be somewhat verbose: Provide some background information about what actual problem the PR solves, why this needs to be solved etc. Don't just provide commits about the fact that you changed something.
If any discussion is needed before actually having any code, simply create a ticket in JIRA or send a message to the corresponding mailing list. Thanks!