How to write an effective but gentle reminder email to a journal editor? I have received an acceptance email of my article from editor in August-2015 and I was told that my article  will be published in their issue of XXXXX 2015/2016. Meanwhile one issue of the journal is published in january-2016 without my article and the next issue is expected in May-2016. Now I am going to write a reminder email mentioning to consider my article for publication in the forthcoming issue. Please guide me or share some gentle format, so that I may be able to communicate with editor well in time.
Make it a question, not a reminder.

I see no particular reason to worry that your paper has been forgotten. It seems more likely just that yours is scheduled for the May issue (or later in the year) because there were enough earlier-submitted articles to fill up the January issue.

On the other hand, asking politely “Roughly when should I expect my paper to appear?” is a completely reasonable question — there are many reasons you might want to know it — and contains no implied criticism that an editor might take offence at.

And in case the editor has forgotten your paper, this will have the desired effect of a reminder anyway.