Are you talking about snail mail or email queries?
If it was snail mail my inclination would be to lay it out like a business letter.
For email I don't bother with contact details, I just add my email addy to my signature. Although, since I live in New Zealand, I always add the fact I am outside the US.
If I get a full request my first page includes all my relevant contact information.
Synopsis are a different creature, it depends what each agent wants. You need to read the submission guidelines for each agent you intend to query.
Some want a synopsis as part of the query, some might ask for it when requesting partials/fulls and others don't ask for one at all