Practice everyday. No time is not an excuse. Make time. Even if you only play one thing such as scales.
Warm up. Just as if you were to play sports. Warming up is crucial to safe and better practice sessions.
Take your time. There is no need to rush practice. Be sure to get the correct notes and relative time values. Speed can be slowly increased once you are confident.
Do not rely on memory (too early). Playing using your memory is great as long as you do not carry any mistakes. It is best to memorise once you have perfected a piece.
Practice hands separate. Simplify harder sections by playing hands separately. However, be sure to start to play hands together as soon as possible.
Keep a record of your goals and practice. Having clear goals and detailed practice record will help you ensure you learn faster. A visual guide to your practice will most likely get you on the piano longer. Use this Diary to your advantage.
Revise your theory. Keep your theory in check. The more theory the better your playing. If you encounter something you are not familiar with in your music ask for help or look it up.
Listen to the Professionals. Find professional versions of the pieces you are playing. Pay attention to tempo, dynamics and over fell of the piece.
Careful with the fingering. The correct fingering can make playing easier. Be sure to take time to develop the right fingering and use the editors suggested fingers.
Practice by sections. Break it up. Take time to perfect the harder sections. Check for repetitions or similar patterns.
Pay attention to everything. Everything on the page is important. From the composer to the smallest dot. Be sure to familiarise yourself with every single detail.
Annotate. Write on your music with pencils, coloured pens etc to help you visualise notes you constantly make mistakes or to highlight dynamics etc.
Practice Smarter not Longer. Shorter more focus practice sessions can be more beneficial than longer session with little concentration.
Practice Away from the Piano. Visualise your music. Think of yourself playing the music. This is also great before exams as a way to reduce stress.
Use a Metronome. Once you are confident in your reading and rhythm. Use a metronome to ensure you are playing in the correct tempo.
Reward Yourself. The brain loves to be rewarded. If you have a good practice session go and do something you like as a treat.
Most Importantly. Have fun. You are learning the play the piano to enjoy it.