A lot of people make piano improvisation a lot harder than it has to be. If you're one of them, this article should help!
Mistake #1 - Thinking about what you're going to play
A lot of students think there should be some kind of preparation before improvising on the piano. They are right! There should be some thought as to the sound, tonality, key - but once these choices are made the thinking should stop and the playing should begin.
Mistake #2 - Worrying about whether it's good or not
Are you concerned with how your music sounds? Many students are. This mistake is prevalent among newbies at improvisation. They play a key or two and then think it stinks. Nothing will stop the creative flow more than thinking that what's coming out of you is not good enough!
Good is in the ear of the beholder. That beholder is you so stop judging the product and focus on enjoying the process of being in the moment. This is why people learn to improvise in the first place. Let go and let the music tell you where it wants to go!
Mistake #3 - Thinking that you don't know enough to improvise
This mistake is really an oxymoron because the more you know, the more likely it is that you will experience blocks. If you do not have a lot of formal music knowledge don't let that stop you. All you need to know in order to improvise is chords and the scale the chords came from. That's it. And the good news is this is easily learned.
Some students create unnecessary problems for themselves because they beleive they need to know this or that before they can begin. This is just an excuse to avoid jumping in the water. It's also a way to avoid the act itself because once you begin to play you may tell yourself you really don't know what you're doing. Trust me. You know enough and you know enough to begin now.