It seems to me that the left engine is "more powerful" than the right, requiring the left throttle to be a little below the right at launch to stop the rocket always turning to one side. I hold the left and right arrow throttle buttons so the throttles are pegged at the top then release them just before launch with my finger leaving the left button just before the right, but so that they both land somewhere in the middle of the green, again with the left just below the right. You can see in my picture how the difference in throttles should be, though I landed them too low in the green at launch. It's tricky business. It takes a lot of clicks of the Relaunch button to get it going straight but that part's not terribly difficult. After launch let go of the buttons and only use them in tiny bursts to steer, as using the engines uses fuel and generates more heat. Use the tiny bursts and keep the smoke trail as perfectly vertical as possible. I think it's best to always reset until the wind sock points straight down. I'm not sure when the best time to ditch the boosters is but do it before they completely run out. Same with the center tank and watch the temp gauge. It seems that you go all Challenger (sorry) about 2 seconds after the temp needle pegs so you have to balance that with the tank fuel. Hopefully that and what I said before about the landings should help you out. More investigation to come from us all I hope but for now I've finished my paper and my bed beckons. I could get seriously obsessive about this.