The idea of “experimenting” with your instrument and your musical ideas is something of crucial importance. In the end, no matter how much direction or lessons we may have, we really all do actually teach ourselves, and this is important to always keep in mind. The art of this “experimenting” may not come too easily at first for some of you, as you may feel afraid or restricted somehow in a way that doesn’t allow you to “think outside the box”, but that is precisely what you need to start doing.
This “outside” stuff I’m referring to is literally that: Think outside the normal positions you’re comfortable with on the guitar! You mustn’t fear any diversion from the norm, since this is really the only way we can broaden our horizons and come up with new ideas. Improvisation is the key to all music, even if we are thinking about composition, since those ideas must also be truly original! Yes, we all borrow from each other, and yes, “it’s all been done before”, but it’s up to you to truly break out of the typical modes and branch out into new, uncharted territory.
To start with, I would say use some trial and error. You can only tune your ear properly with hearing some “wrong” notes along the way, and once you’ve actually made those mistakes, you’re far less likely to even make them again. One thing is for sure, you never want to become the kind of player who somehow keeps on memorizing their mistakes, which believe it or not, I have encountered quite a bit in my lifetime! This can be especially frustrating when a bassist is somehow doing this, and they manage to keep on falling into the same mistakes...usually because they are “predicting” changes, as opposed to really and solidly learning them.
A good way for you to also break the creative ice is to experiment with chromatic runs. A chromatic run, where you are not skipping any frets, can almost never be wrong, as long as you don’t lose sight of the notes you are shooting for. For example, if you’re running chromatically from B to A, you never want to get too hung up on the A#, as that would be far too dissonant, and would simply not make any sense. Remember, when we listen to a guitarist improvise and experiment with new ideas, we are literally hearing their thought process, and when that train of thought is broken, the listener no longer wants to tune in to what you’re doing!
So, experiment, elaborate and discover....and hopefully, along the way you’ll be able to tune that ear of yours to know what works and what doesn’t! It’s a lifelong quest, so better get going!