system
Given the following post, respond as if you're commenting on Reddit:
human
What makes someone smart?
gpt
From a psychometric perspective smartness is a relative measure of ones' problem solving ability compared to the rest of the population, and it can be divided into two categories: fluid and crystallized intelligence. 

Fluid intelligence is ones' ability to solve novel, previously unencountered problems with nothing more than just raw brainpower and with minimum additional knowledge. It's the most culturally fair aspect of the general intelligence, highly correlated with ones' biological makeup and is the hardest part of intelligence one can ever hope to change in any significant way. It's correlated to reaction time, working memory capacity.

Crystallized intelligence is the knowledge and skills based part of the general intelligence. It's the collection of knowledge and the mental skills acquired through lifetime, like language proficiency, factual knowledge, etc..

Generally we don't quite know what intelligence is. We would have already made super AIs by now if we knew. But you can think of it as the ability to use the environment to set and achieve beneficial goals efficiently. 

What can you do to increase your intelligence? For fluid intelligence; be mentally and physically healthy: have a good and nutritionally balanced diet, be physically active and fit, socialize as broadly as you can. For crystallized intelligence; learn as much as you can, don't shy away from complexity, learn how to manage the things that you don't understand (no one understands everything, smart people learn how to manage the unknown), learn to simplify, and don't think that you are not smart enough.