Hemming jeans the easy way ~ I don't like the method of re-using the original hem and sewing it back on. This seems to be a good method without the bulk of the flat felled seam. Serge or zigzag the bottom edge, turn it up ONCE, then hem.
Alteration: My new favorite way to keep original hem on jeans
I used to do this to my girls' jeans after school let out. Great way to boost the summer wardrobe for next to nothing! Transform an old pair of jeans into adorable summer shorts using bias tape. Instructions on the site.