Make sure you have a good reason for the check. It will only be accepted to counter vandalism or disruption to Wikimedia wikis. Valid reasons include needing a block of the underlying IP or IP range, disruptive sockpuppetry, vote-stacking, and similar disruption where the technical evidence from running a check would prevent or reduce further disruption.
Be specific in your reasons. Ambiguous or insufficient reasons will cause delays. Explain the disruption and why you believe the accounts are related, ideally using diff links or other evidence.
Make sure there are no local checkusers or policies.
Reason(s): A while ago user Barselona99 was blocked for serious reasons (talking rough with the users, downloading files without license and source, using non-Azerbaijani characters in articles etc.), even we had discussed about this. After this new user appeared, Barçamaniya. The nicknames and writing styles are very similar. We have doubt that they are same users.White DemΩn(el psy congroo) 10:04, 10 December 2017 (UTC)
Likely the same user. There are other accounts Likely belonging to them like Azərbaycanın şəhidləri. Ruslik (talk) 18:29, 11 December 2017 (UTC)