The answer to this question, if done right, would probably not fit in this small little text box. So, in no particular sequence:
1. Romance all those who can be romanced.
2. Kill all those who can/should be killed.
3. After doing the above, reload and side with the bad guys (Hey, we all have to satisfy the dark side itch, once in a while!)
4. Hack into anything that can be hacked (AI AND human/humanoid!)
5. Walk, ride, take the train, fly to all possible destinations.
6. Lie, cheat, steal to become the richest SOB in the game . Then reload an earlier save, don my halo and attempt to be a cyberpunk-ian role model (if that's even possible)
7. Finally, become the world's meanest, weapon-trodding, hacking, drugged up son of a gun that causes NPC's to tremble in awe and their AI's to defrag as I walk by them (the question never said one has to be realistic OR reasonable, right?)