I think first you must identify who they are to you. A sibling (3H), a potential lover, or a child (5H), a work mate or associate (6H), a committed partner, competitor, or unclassified 'other' person (7H), a boss, or perhaps even a parent (10H), or a friend or social aquaintance (11H)...there are other possibilites, but I'm not so clear where to put them, so we'll start with these. Does the person fall under any of these categories?
You will also need to look at your own third house (the natural third house) and the 'turned' third house (third house counting from the 'other' person's first house). The natural third house relates to your communications and received information, the turned third house to 'their' communications and received information. Hope that helps a little