METRONOME HELP!

I use to study guitar with a metronome..Let's say i start a chromatic scale at 120..how i'm gonna increase next?:126 or 132 or 138 or or or e.t.c .I hope you understand what i'm saying!

You will have to custom-tailor your routine to suit your individual abilities. Stepping from 120 to 126 might be too large a step or not enough. If you can play the scales, arpeggios, or whatever, cleanly at the new setting, but not as well as you can at 120, the increment was good. If you find that your playing is sloppy at the new setting, you will need to reduce it a bit.