Vivian Siegel stressed the following lessons on interacting with professional biomedical journal editors.
The editor must believe that your paper will increase the impact factor for that journal.
The editor must be able to easily understand what is new in your paper and why he should care.
The presubmission inquiry should summarize your study in one or two pages; include the abstract and why you think that your paper would be appropriate for that journal.
You can and should do this before the paper is finished.