theres couple of steps before u attack a computer, network, site etc...
First off You should Fingerprint them and learn as much as possible http://packetstormsecurity.nl/papers/general/Footprinting-faq-v0_1.txt
U should connect to gateways so you wont get caught that easly
when u actually do get in, always remove EVERY trace possible so u wont get caught
here are to GREAT papers written by Van Hauser of The Hackers Choice (THC) group http://www.thc.org/papers/COVER-1.TXT http://www.thc.org/papers/COVER-2.TXT
Remember never go in blind, or you will prb get caught and blamed for thousands or millions of dollors worth of damages because u simply loged in.
before u start bruteforcing make sure u have a nice big wordlist so you actually have a chance of breaking user/password
heres a link of A LOT of wordlists http://www.phreak.org/html/wordlists.shtml