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): Same disruptive edit pattern (mainly recurrent copyright violations and missing source quotations, producing junk pages). There might be more accounts of the kind and there is reasonable suspicion that they are sockpuppets from a huge clone farm maintained by Beleiutz years ago (too old to be checked now). -- Victor Blacus (talk) 16:10, 26 March 2017 (UTC)