Selection of Indexing site for an international journal depends on journal content. So before submission of journal to any of indexing portal international journal should list following set of parameters:
All above information are cross check by the indexing site. As most of points are basic and improve immediately by the publisher but arrangement of reviewer team and good publication is time taken process, so I suggest that good indexing platforms do not accept new journals having life of less than 3 years this period is enough to publish only good papers with knowledge full reviewers. It was suggest for editor to do communication by email with authors as any of data requirement is always trace by the emails.
So basic search of How to index my journal is resolved under following heads:
Number of volume/ issue in a year
Publication medium Online, Offline
Special issue / Conferences Details
Indexing on other portal Links
A reviewer list as per their expertise
Indexing sites of journal are independent body they can list any journal and remove any journal without any prior information so its an request to journals that always follow rules or policies of good indexing platforms and maintain journal indexing. I suggest editors to always select indexing sites that can list journal and its papers as well so that they can also get popular between other researchers that ultimately increases the citation count of paper and journal.