I'm currently in the middle of some calculations and modeling for two related but different papers on experimental and data analysis mathematical techniques, and have started drafting two papers.
Depending on how they fill out over the next few months they may or may not be best suited for the same journal.
Each paper and its readers will be best served if it references the other, and this may be in fact necessary to avoid having to have duplicate sections and trying to do extra work to make sure they are also sufficiently different that they are not copy/pastes of each other (i.e. avoidance of self-plagiarism?1).
The topics are sufficiently divergent that they really can not be combined into a single paper without it looking like two papers hastily duct-taped together.
Question: What are the ins and outs of submitting two related papers that need to cite each other to the same or different journals? Any potential pitfalls I should keep in mind?
1 Using same text in different papers sent same time? See also "Is there any reason why your papers can't cross-cite each other?" and "You can actually cross-cite papers that are 'work in progress', especially in initial submissions."