theres a few methods to improvising.
some of the obivious one are,
1) improvising with rhythm
2) with the native scale
3) chord approach
it also depends on the style of music you play, for jazz pros normally knows the different type of scales like aeolian, dorian, lydian, etcetc. and they improvise based on the chords. AND NO they dont just use the chords to improvise, with some solid rhythm added to it, they can use one motive and go on forever!
however if you do not have such knowledge, you can improvise using the native scale, find out the scale you are playing in, use melodious line to improvise. if you are comfortable already add in some rhythm. remember improvising is about getting the motive and the groove once they are register in you, you can improvise better
well my thoughts might be wrong man.