I'm sure others will have different and or better guidelines, but this is what I do for conventional, side of rack, break shots:
1) If the cue ball is closer to the side rail than the break ball, I use follow. I stroke it enough so that after hitting the pack, the cue bends forward and rebounds off the foot rail.
2) If the CB is further away from the side rail than the BB, I typically use a little draw but I also look to see where the tangent line intersects the rack. If the tangent lands on the extreme top side of a ball, I may just hit it with center. If the tangent intersects the outer most point on a ball, I will definitely use draw. If the tangent intersects the lower part of a ball, I may consider to follow to hit the lower ball or I may hit draw.
3) If the CB and BB are the same distance from the side rail, I feel that this is the highest chance of getting stuck to the rack and usually play the shot with a little draw and a little outside English.
Most importantly, you need to set up shots over and over and experiment and figure out what works best for you. I know it's cumbersome to keep reracking, but the shot is so important it deserves this kind of attention.
Just my two cents.