I constantly use my reminders app on my phone/computer to ping me to get certain things done. As for paying attention, maybe you could try finding a small fidget—I know fidgeting helps a lot of people, myself included. The memory thing is a lot of practice. I did it through colour coding. Each coloured pen/highlighter/sticker/etc. was given a labelled meaning. EX: red - important test info; blue - vocabulary; pink - my opinion; green - questions/ask about later.

I use fidgets to pay attention in class

I had to find a way to overcompensate for not being able to stay focused on things like reading. I could pay attention in class if it required physical movent..in other words I learned only when I had to do something...take notes is physical. Writing vocabulary and definitions over and over. Forcing myself to make a game of something to recall...ie an appointment on Tuesday at two is a tutu( ha ha but that game is over compensation and helps). I learned to disguise my symptoms because I knew something was wrong with me. I believe too that just as a blind person hears better, a deaf person has better vision, an adhd develops something. Medication really works better than all the time spent for overcompensating.

writing down something you think will be important is key, because once you write it, recite it, say it out loud to yourself when you can to tell your brain the information verbally. paying attention is still a big thing for me unless in genuinely interested, so when youre in the middle of a boring lesson give your mind some stimulation like doodling in a notebook or (personally) ill set my foot on my chair at school and play with my shoe laces