Right/Down/right/Down with an Up/Right/Down thrown in when stuck has worked well for me. My first 1024 block came that way.
When I began playing I was moving around the board in an unorganized fashion, but am now finding that moving the larger numbers to one corner (bottom-right for me) is the best method. By having your block consolidation take place in one particular area, the odds that you'll have matching large numbers goes up dramatically.