Key of Song

Ok, again, here we go.
Nobody even began to answer this question the last time, im not being bitchy but its answers i want!!
How can you evaluate the chords being used as a key, so you can then work out what key to play an improvised solo in?
Later Axl

one easy way is to count the sharps or flats that are repetitive in the chords. if there are 2 #s yer in D. one flat is F. ya know the circles of sharps n flats ? sometimes the chords kindo step outside o the normal theory structure so ya can , if ya see 2 major chords a step apart, hope to assume that the higher one is the fifth of the key ( if ya see a C and a D assume its in G )i always try to see it as in the key with the fewest incidentals.
ya know ? them notes that ya only strike in passing on occasion but are not 'in' the key ?:)

You can do that, or you can just look at the notes of whatever particular chords are being played and figure out which scale would contain those notes.

Example - if you're playing the progression G, C, Dm, you'd play in G mixolydian (C major), because the Dm has an F note. If you were playing G, C, D, you'd play in G major because the D major chord has an F#.

Ok, this is good, nice advice, I'll learn about the circle of flats and sharps
Last sat i was jamming with apal and he noticed i was soloing in the correct key, he said "wow that fits" too right!! i just played on the C Major pattern, well cool.