Basically a mirror image of http://www.sexyloops.com/flycast/double-spey-45/
Remember: as in all casts there is a target behind you. At the final moments of setting the D-loop you should attempt to poke the rod tip along a straight line to this target. This target, for any straight line cast, is always diametrically opposite your forward target. The rod is canted (tilted) at the beginning of the forward cast, because the anchor is placed off-shoulder, and just as in the simple roll cast, the rod tip should be directly above (or more accurately slightly inside) this anchor. And finally because your rod is canted at the beginning of the forward stroke, it follows that it must remain tilted throughout the stroke.

To summarise: Spey Casts are change of angle dynamic roll casts. The Double Spey is a “waterborne” anchor cast. It is most useful for sink-tip lines and heavy nymphs. In river situations the Double Spey is used for downstream winds. There are essentially three movements; the first movement is to lift the line off the water and sweep the line upstream placing the fly into the correct position. The second movement is to sweep the line downstream of the angler forming a D-loop, off the shoulder, aligned to the forward target. The third movement is to deliver the fly using a roll cast.
The 90 degree Double Spey is easy. The 45 degree Double Spey lends itself to inefficiency by placing the anchor a long way in front of the caster. This can be dealt with in certain ways: 1) cutting into the bank on the upstream Sweep, 2) finishing the dangle with the fly closer to the bank or 3) repositioning yourself into a position so that the fly is closer to the bank than you are (see: http://www.sexyloops.com/flycast/double-spey-45/ ).
Later on in this series, you will see that there are in fact other options, from starting the Double Spey with the fly closer on the dangle and slipping line during the Sweep/s, to making “pokes”, to aerielising some or even all of the movements. But for now, if you haven’t, you need to master the basics.
Got a question? Try asking here on the Board: http://www.sexyloops.co.uk/theboard/viewforum.php?f=82
Or drop me an email: paul@sexyloops.com
Cheers, Paul