Consider source. The source has a lot to do with the antibiotic. It is common to use a third generation cephalosporin and/or a quinolone. Vancomycin is an option if resistant staph is possible.
Depends on bug. Gram positive cocci can occur in pairs (usually pneumococci), chains (streptococci or enterococcus) or clusters (staphylococci). Empiric therapy depends on the type and whether the patient has penicillin allergy.
See below. One of my hospitalist colleagues will hopefully chime in on this one. Without knowing any details I think the patient should be covered for MRSA (methicillin resistant staph aureus). Therefore the following would be the best first choice: vancomycin ± gentamicin or rifampin. When further data comes in from the lab on the gram positive cocci then a different antibiotic might be a better choice.