How I started: adapting from app Mahjong to real-life Mahjong

I looked up a Japanese Mahjong app to start experiencing and choosing an ideal discard. I used an English app, Mahjong Demon Lite, instead of the Chinese/Japanese ones commonly used in my country, Singapore. I found this worked very well for me as a new player getting a feel of the game, but it might not for everyone, so I'll detail its pros and cons.

Pros

1. There was no time limit as it was against Computer AI, so you can think for a long time on which is the best discard that maximizes tile efficiency.
2. The absence of a time limit also helps you decide whether to open your hand with Chi/Pon/Kan, or keep it closed. This is important in deciding the direction of your hand.
3. There are helpful star-indicators for which tile is the dora, your round and seat wind, and the yakuhai. This feature can be toggled on and off.
4. The discards were not sorted properly in 6-tile rows, which gets confusing when you switch to real-life playing.
5. The app shows you every possible discard when you are in Tenpai and about to declare Riichi. This helps new players learn the many different directions a hand can go to depending on the discard (e.g. whether to choose a more efficient multiple wait, or a different single/shanpon etc wait based on discards or what you anticipate your opponents' hands to be)

Cons

1. Computer AIs are not a realistic depiction of players who go against conventional plays of maximizing tile efficiency. When you gain experience, I would recommend playing against real players on Tenhou.
2. As with most apps, there will be an option for you to Chi/Pon/Kan/Ron etc. This makes it hard to adapt to real life playing where there isn't that indicator.
3. Showing you every possible discard at Tenpai is a learning handicap. Recognizing these possibilities in real-life is important.

It was a fairly unsystematic style of learning. I gradually supplemented it with more knowledge of the game.

First, knowing your yaku. See ofb or wikipedia. I skipped yakuman hands but went back to it later.

• Supplementary readings: arc.su yaku compatibility

Second, understanding fu count to maximize small yaku hands, or choosing to deconstruct a large yaku hand when defending against opponents and still maximizing score.

Third, understanding wait patterns, both simple and complex.

• Having a good multiple-wait is helpful during Riichi, but even a simple wait 

Fourth, maximizing tile efficiency, while remaining discrete.

Fifth, when to Riichi or not to Riichi. (beginners generally Riichi immediately on Tenpai)

• Do you want to build your hand further? Is it more important to win early?
• Is it dangerous to Riichi? Will you just be feeding your Riichi stick to your opponent?

Sixth, playing with a tenacity to gamble. Know when to switch between Offense and Defense.

Seventh, manipulating your opponents through discard patterns.

And finally, reading your opponents, through discards and reactions, but never over-read.