If a child is always wanting to stop practicing after 5 minutes or so, there is another problem at hand that is NOT likely a character flaw in your child. Most often, it is a teacher whose personality doesn't match the student, material that is not at a proper level of complexity or musicality, or fears/ social anxiety about playing the piano in general. Less often, it could be a physical problem with muscles, coordination, or eyesight.

A great way to help you memorize a song is to play it right before you go to bed. You have more chances of it turning into long-turn memory because it will be the last thing on your mind before you go to sleep. If you practice earlier in the day though, it will often turn into short-term memory because of the daily overload of other tasks that are done throughout the day.

Playing something is better than not playing at all. So, yes, if the only thing you can bear to play is "Moonlight Sonata" or "Memories", then go for it.

Try to "underachieve". Got this idea from Robert Kiyosaki who I think got it from someone else. Say to yourself, "I know I should probably play 30 minutes each day, but I plan to do at least 10 minutes a day. I know I can do at least that much. Then, stick to it. You'll find that you practice more than usual!

Be sure to strike the keys fully, creating as much of a full tone as you can, rather than just barely getting any sound.

If you've had any piano lessons, you probably know - play with the tips of your fingers, not the "pads" of your fingers.

Barlines are simply a way to break the piece into manageable rhythmic increments. Don't think of them as a destination. If anything, they are a springboard! (other than a double-bar line at the end of the piece)

While you may think that, like typing, it is best to arrive at the point where you do not look at the keyboard, you can improve your technique by looking at your fingers as they play at times.

When sightreading (reading a piece of music for the first time) - try to play at a slow enough tempo that you can keep going without stopping. That is the goal.

Would you believe that memorizing a piece can increase your sightreading ability? Your brain catalogs the different motives and passages and you'll have a better shot at playing them correctly should you see them again in a different piece of music.

Be aware of the relative strength of your different fingers. You may have to work a bit more with your pinky to match the sound of the notes played by other fingers in a passage.

Be aware of what piano techniques are style appropriate. I once played with a budding jazz pianist who at the time had the odd habit of using a honky-tonk tremolo when we played a blues. He grew out of it, though. : )

What you are sitting on can affect your playing. A padded, adjustable piano bench is wonderful for your playing and your back. At the minimum, try to get something at the right height, not a high bar stool for example.

Lighting can be key to a good practice or performance area as well. It will keep you from bending and contorting in order to see the sheet music.

Don't negate the idea of purchasing a used, older piano, especially one that is pre-WWII. They can have a marvelous sound, and can sometimes be had at a bargain, even after paying for minor or major repairs and refinishing.

True ivory from Elephant tusks can only be found on older pianos as it is now illegal due to poaching. If you can find a good piano with ivory keys, the feel is said to be the best. An alternative would be taking the ivory off of an older piano that will be scrapped.

Keep a fug under your piano. It will dampen the sound a bit and help regulate moisture.

Have people downstairs complaining about the volume of your playing? Try putting casters or rubber pads under the piano legs.

Modulation: moving from one key to another within the same song (not just playing a song in a new key altogether).

Accompaning or playing from a "fake book"/ improvising? Voicings can make all the difference. If you play every chord in root position, your accompaniment will sound robotic. Experiment!