Attend college coursework.
Spend too much time on Agnostic.com
Read articles I don't fully understand about quantum physics
Do things people say I can't do

I read a lot too and I love that we live in the age of information. If I want to learn about literally anything I can, right from the comfort of my own home. I also subscribe to certain youtube channels (like "SciShow" and "Today I Learned" ) that have taught me some interesting info. I also enjoy video games where you have to solve puzzles and I do sudoku every now and then.

Watch Seinfeld reruns on TV.

This site spurs me to look up things I never did before. THen there is the NYT sunday crossword puzzle

Teach

At 84 years of age .......I...do gardening, fly using simulators on my computer,, Write articles on safe driving, explain how we see from light to sight, explaining floatation, illustrate relative sizes of our planets, For interest I board Chinese folk and befriended about14, [ The ladies are delightful ! ]
photography, made 8 and 6 inch Astronomical telescopes, manufactured both parabolic mirrors, made a 5 stage mechanical seismograph, working on making electronic devices, go gliding occasionally, read books, watch interesting programs on the TV, learning German , sketching, I love helping other drivers on the road, microscopy, was Paragliding, was catamaran sailing................................, was a total dropout at school..............., Auf Weidersehen.

I use Duolingo to learn new languages. I am revising grammar through Khan Academy. I use MOOCs (Future Learn, Coursera, EdX, Udemy) to study subjects of interest. I am learning Python. I write poetry and I am working on a series of novelettes (I have written two so far). I also play computer games.

I read. I sing. I play the piano. I have conversations with intellegent people -- including, now, on this site. I read in French. I knit and crochet, following complicated patterns and doing a lot of swearing. (Swearing keeps your brain active, right?)

I don't read books like I used to-like to challenge my trivia knowledge by competing, playing Jeopardy and playing word games.

I read alot and belong to a science fiction book club. I have an 8 year old daughter who I love to take to museums (nature, science and art museums are our favorites). I do most of the maintenance work on my home and cars. My work as a software engineer also keeps my brain somewhat engaged. I also stay very physically active, hiking, camping, mountain and road bike riding.

I color

I work in IT consulting management, like herding very smart cats, breaking up fights, coaching, therapy, and mediation.

I am building a wooden boat for the winter project, and have not yet cut off any fingers. This is a true learning experience as I have not worked with wood for 40 years, and never built anything this huge anyway. I also get to learn how to sew as I have just ordered the sail material.

I took a different position at the company I've worked for the last seventeen years. I'd been in the I.T. field prior and now I'm a distribution service operator. I plan/write switching orders to route power around our section of the grid for maintenance and in emergencies. I'm always surprised by how often people run into poles with their cars! And fun fact, squirrels are apparently natures nihilists. It's a three year apprenticeship and I just completed the first year. And yes part of my motivation was to learn something new and hopefully keep my mind sharp. I also read although I find I don't have the attention span to devour a book like I once did. Games of the board, card, and video games are big in my house. My kids and I play D&D on Thursday nights. We play Magic the Gathering as well but that's taken a back seat to D&D at the moment. I'm into 3D printing, woodworking, I'm a big fan of DIY anything. My dad was diagnosed with dementia before he died so that has motivated me to ratchet up my self care. Oh, and I tend to have long winded answers to questions on Agnostic.com

Listen to audio books, podcasts, and debates while I go out on drives or walks around where I live. Kills a lot of time, and any general discussion of philosophy or science is especially sobering while I walk about the woods and along the shores.

Occasionally read, but not to any great extent unless it is something I am invested in or looks interesting. Otherwise I just play video games as well, ones which usually require a good mastery of their mechanics and not super simple things.

I read, write, and learn new skills.

It's not why I do it but i play music. I'm sure I've read somewhere of the many benefits to the brain of learning an instrument.. maybe, like the Xtians, I just get comfort from the idea and so choose to beleive it.
I play banjo and squeezebox and am currently learning flute. I practice a lot and every morning I think 'what am I taking to work with me today?' (First world problem, huh? )
Today it's my banjo and the flute.
DISCLAIMER: PLAYING MUSIC AND DRIVING A TRUCK SHOULD NOT BE UNDERTAKEN AT THE SAME TIME!!!! I play when I'm pulled over taking my break (mostly )

Sudoku. But I also research in 2 main historical crevasses, and listen extensively to various podcasts. Oh, and of course my job which requires technical creativity...

I adopted two chihuahuas who are obviously smarter than I am. Keeping up with their shenanigans cranks up my brain cells. I am writing my memoirs in the Palm of the Hand style that requires lots of thinking and editing.

In this past year I've spent a fair amount of time learning how to trade stocks.

Draw, sculpt or diy

Puzzles.

I want to know everything, if I lived for ever, my goal would be to know and understand everything. Even now I take on new projects every day, some would be so simple for others, but to me they are new. Disappointing thing is that of course, nothing I learn is new, it is already known, and when I die, it has been a wasted effort.

You think. You are constantly seeking new, valid information from any available and reputable source. You keep weaving that new info into the cognitive patterns you have already developed. You discuss issues with curious and open-mined people.

I read, write, and workout everyday. No excuses. Make the cranium dance