Here are a few resources for you:
www.fltplan.com for filing flight plans and getting weather.
NBAA for information, questions, and great help for the corporate pilot.
CAMP systems is a great maintenance tracking program we use, tells you what maintenance is coming due when, lets you track numbers such as cycles, engine time, etc. in conjunction with maintenance.
Get to know the aircraft maintenance people. If it's your in house people or an FBO you use. Get cell phone numbers, e-mail addresses, and just stop by and chat every once in a while.
Do some research into the airplane. Who owned it first? What kind of quirks does it have?
Also, as far as W&B goes, I totally disagree with the "some people use it, some don't" attitude. While it may be true, it is so easy now-a-days to either make a W&B program in Excell or get one from any number of companies that you should do one for every flight. It's your ass on the line if you run off the end of the runway because the boss wants to take all his buddies and golf clubs plus full fuel. Know the airplane, what it will carry and what it won't.
Feel free to PM me with any questions. I am just like you, came from 121 and am now managaing an airplane for a company. I'd love to help. Good luck!