Step 0: Make sure you have full health and armour. Stock up on projectiles if you are planning to rampage on a roof (grenades or molotovs as flashbangs and proximity mines will be no use to you at all while on a high roof).
Step 1: Get a bike, preferably a chopper or an angel, because a sanchez and an NRG900 will almost always blow up on contact with the gas tanks.
Step 2: Get to a gas station which has space to do a long drive up to it, moderately fast or enough space to do a burnout.
Step 3: Drive moderately fast, or do a burnout closely to the gas tanks and hit a gas tank with the side of the bike, (do not drive head on into a gas tank or you and your bike will blow up). You should be soaring through the air with the bike on fire, time your jump before your jump before it blows up and you might land on the roof. Do not worry all roofs close to gas stations (the only ones I tried) are clipped for some reason and you will not fall through (it's like they wanted you to do it).
Step 4: (Depending on the height of the roof you're on 45 - 60ft) You will be able to see the draw distance of the map, (where it goes grey after the roads end) Objects on roofs such as billboards and water tanks are not clipped. But the whole of the roofs are and the gaps in the roof are clipped over so you cannot fall down them. Falling from any height will not take any health off you because you were not intended to be able to fall more than one story off a building.
Step 5 [Rampagers only]: (This really depends on the height of the roof you're on, this applies to 45 - 60ft high roofs) Once on the high roof you cannot shoot people below you because you are too high up and your bullets will stop halfway towards the ground, a sniper rifle would be really handy here). You can throw grenades and molotovs down until you are at a 6 star wanted level if you want, but helicopters start coming after you at 3 and you can shoot them down with any strong weapon. Because the cops cannot shoot you with their pistols they will instead continuously reload their weapons. Mess around on top of the roof and try to get a really high time for a 6 star wanted chase. Also note that cop cars trying to get you may just smash themselves into the side of the building and you may start losing stars.
Edited by Reconite, 09 May 2009 - 01:19 PM.