I use my interpretation of the Tanabe-san sequence. First I braze the fork to get a definite fork lenght value. I mitre all the tubes and add the braze-ons. Next I braze the TT-HT, then tack the TT-ST and adjust for twist if necessary. You need to properly locate the TT intersection point and phase the BB mitre. For a fillet brazed bike the shell is tacked (tinned at the front quadrant). Next I check the DT fit (it may need minor adjustement) and tack it at the HT (and the BB if doing a fillet brazed bike). For a lugged bike I hold it to the ST with small & strong magnets. Then I braze the ST-TT and DT-HT and finish with the BB. Then the chainstays and finally the seatstays.