My advice is to go out easy and get PROGRESSIVELY faster. Some hear "2 Laps" and decide to go from 50% to 100% on lap 3. Make your increase in speed is progressive, a little faster every few corners. That is how I like to think of it at least. Tires ran at 50% for 2 laps are hot enough to go faster than 50% on but are NOT ready for 100% or even 90%. If you start out at say 50%, give it half a lap and go to 60% for half a lap, by the end of lap 2 you have pregressively gotten up to maybe 70%, a few corners at 70% then go to 75% for a couple corners...