What is a simple way to determine the notes in a scale?
For example, let's say, that somehow you determined that a song you want to play, is in the key F# major. How can you quickly recall or figure out the notes that are included in the F# major scale?
I have heard that there is a system to do this quickly, called 'the circle of fifths', such that you don't need to memorize all scale variations for the various keys and the notes in them - something that I found very difficult to learn, remember, and understand.
Added. Guys, I'm deeply sorry for asking such general and non-concrete question. I want to add a bit of information for you to understand what I want. Me and my friends have a tiny garage band. We love to jam together. Sometimes we play before an audience.
I know how major and minor scales are built (relation formulas), but that don't give me a lot of help when we jam in a key which is not C (major) or A (minor), and I do a lot of mistakes (by hitting a wrong notes, which are not in the scale), which are quite noticeable by bandmates and listeners. Well, of course, after some time, I realise which notes sound good in the selected jam, and I am able to build and play proper musical phrases (in selected area of a fretboard). But when, for example, I hit the note far from phrase played before, 90% of time I hit the wrong note. And that's causing a little stress. -- well, I'm a bit an overstating things here, because really, I use some tricks, like, as you know, on a guitar fret, some intervals form a pattern, like, for example, perfect fifth, which would be played the same, and which are irrelevant on the key you play, like in C perfect fifth would be played the same as in the F# - you just remember the finger pattern, that all. --
All I want is to simply to avoid such thing in my playing. That's what I'm asking - is there any way to "see" literally on a guitar fretboard the right keys, and how even to remember them all, because, as we all know, there's a 12 variants for a minor scale and for a major scale (from key C to key A, including all alterations - that's said, C, C#, D, D#... wonder how to memorize all that ton of info).