There are multiple possibilities, not necessarily good ones, however. It is recommended to use an air compressor if possible, to avoid damaging your computer. Some possible methods include: taking out the heatsink and cleaning it with a brush, using a silicone blower as a cheaper alternative, using your vacuum cleaner, reversing it to act as a blower, and using a hairdryer. Probably the best alternative is described in the step guide presented in this article... using a cotton swab and rubbing alcohol to clean as much as you can.