Start on a LEVEL FLOOR, take a 2 foot level and lay it against the tire (sidewall) 90 degrees from the ground (up and down), use the shims necessary to get the bubble in the center or just slightly to the inboard line. I would double check my toe with a tape measure getting it 1/8-1/4 inch tighter in the front (toed in). This should be a safe driving setting to get it to the alignment shop, but test drive it for stability and drive straight to the shop at a moderate speed. I will usually double check my settings 3 or 4 times just cause I'm anal and I kinda pride my self on how close I get it.