Late reply
If you haven't gotten one yet, read up on cat ownership before you get one.
Important rule - NEVER LET YOUR NEW CAT OUTSIDE FOR ANY REASON WITHOUT SUPERVISION. If they're unused to the surroundings, they may get freaked out and run away. Better, use a torso leash, the one that goes around the legs as well as head.
If the shelter/previous owner hasn't already, drop some Revolution on him/her
http://www.revolution4cats.com/
It will kill off any fleas or mites currently residing on her body. Don't shower a new cat first, most cats hate it and it's not a good first time impression or bonding experience. Use baby wipes instead. They're gentle and hypoallergenic and suitable for use on cats.
Put a box in her room with some newspapers in it and let her settle down some first before you introduce her to her surroundings.