Well, there are many many how to’s online.  here are some things I recommend
1). when the chips at its hottest “DO NOT TOUCH IT WITH ANYTHING” if that thing moves I’ll bet you have a scrap board now unless you remove the chip and have a reball kit.  Some times the chip is glued at the sides or corners so the chip will not move, (nice) see the red

thats the one we're after

 
2). make sure the board is level. if the board is on an incline hot solder runs. maybe not fast but if you see a small silver looking bead at the lower end of the chip you’ll know better for next time.

3). you can do the reflow with a large hot blower but your chances are lower for success. your better off finding someone with a rework station you can borrow or find a hacker space you can be a member of. I expect them to know where there is one.  Rework stations have controlled temperature and air flow rates which make it easier to follow charts.

charts are google-able under solder reflow

4). why do it by hand when you can use a stand

make it adjustable

5). use a clean bench to spread you laptop parts out in the order you pull them out so you can remember how to put it back together. Start by removing all roms, memory and other detach-ables. Watch for easy to rip ribbons and hidden clips and remember to go slow.

6).when you put the laptop back together, take extra precautions to make sure the chip remains cooler to ensure that you don’t have to do this again. So clean out all the hair and dust and add what you must

7). always test the laptop before you pull all the screws back in

anyone have a line on an impossible to find LG r500 laptop video card