A: There are two ways:
While in-game open the console using the ~ key and type status in the console.
Locate your steam directory on your hard drive, usually C:\Program Files\Steam -- find steam.log file and open it with notepad. Look for lines such as: Found existing connection 9,184.108.40.206:27030 for 0:0:8888. The last few numbers is your steam id, ie: 0:0:8888.