How can an igneous rock become a sedimentary rock?

Question

How can an igneous rock become a sedimentary rock?

Answer 1

Imagine if you took a chunk of igneous rock (e.g. granite) and smashed it into bits with a hammer.  Then you took those little bits and smashed them into even smaller sand-sized particles.  Then you take these sand-sized particles, dump them into water, cement them together, and let them dry - Presto! you got a sedimentary rock.

The process described above is more or less what water (and to some extent, frost wedging and wind) does to break down existing rock into sand.  However, water doesn't generally carry around hammers.

Short answer?  erosion, transportation, deposition, burial, cementation  

How?  water and lots of time