How to Play TriadCity
The TriadCity Players' Guide
Tips & Tricks: You can Increase Your Attributes When Leveling
For instance, warriors might want to beef their physical endurance. So if they raise their Constitution attribute while leveling, they get a perk.
Another example is Intelligence, which increases the number of practices you'll receive for that level. The higher your Intelligence, the more practices. (You'll want your Intelligence as high as possible while learning Skills, also.)
How do you raise your attributes? Usually by wearing some Item which impacts that attribute. For instance, bracers will add strength. You might also try eating certain foods, drinking certain drinks, and so on. It's a good bet the "smart juice" is named that for a reason. Ask the higher-level characters for any tips they might have, most of them will be happy to share.
Some players look at these bonuses from an oddly reversed perspective. They consider themselves "penalized" if they're not accessing these attribute enhancers at the moment of level. We disagree. These are perks, not necessities. Life will go on just fine if you ignore them. Or not. Up to you.