MacBook systems have a notorious reputation for running hot when put under heavy load, which can make them uncomfortable to handle. This is especially true with older MacBook Pro systems from 2009-2011, where in comparison to the latest models that have vents along the side, the lack of vents causes them to run hotter and have internal fans work harder to pump air over the system’s heat-sinks. If you are sick of your Mac getting too hot, then one effective approach you can take is to open it up an drill yourself some new vent holes.
The main cause for extra heat is from the tight spaces in the MacBook that confines the heat, and while opening the system up will obviously give you the best options for cooling it, this is clearly not a practical solution for a laptop system.
An alternative that the folks over at iFixIt have undertaken is to provide their own vent holes in the bottom of the system, to give the fans a quick intake of external air, and allow them to pump this cooler air over the system’s components far more efficiently, giving making the system run cooler without constantly ramping up the fans to their highest.
Since the Mac’s aluminum chassis is relatively soft and thin metal, the area around the holes you drill may warp if you press hard when drilling, so be sure to go slowly and with low drill speeds, and allow a fresh and sharp bit to do the work (drill on a piece of wood for stability and safety). If you drill from the outer side of the panel then you can help avoid burrs, but you might still need to gently sand the area to reduce any sharp edges. Be sure to thoroughly vacuum all metal shavings and shards before reassembling your system.
Keep in mind that while this is doable and should work very well for any Aluminum MacBook, it is a more radical approach that will void any warranty. Therefore, be sure you only do this on systems that are no longer covered, and only if you are experiencing problems that you cannot otherwise manage. In the case of iFixIt, the issue was from a long-standing graphic problem where poor soldering on graphics chip components in older MacBook Pro systems would fail under use from excessive heat.