I use foam mats from ELC as my blocking surface but you can pin out on a bed or on a clean sheet on your carpet (Or you could hoover!)
I like the mats because once pinned out the lace can be stood on it's side, the mats are interlocking so you can add more for a larger surface and when using heavier yarns being able to move the blocking to another room is a big advantage as it may take many hours to dry. This project is in a 2ply laceweight Posh Yarn Eva so it'll dry quickly.
For blocking you also need some pins (T shape are easier but any rust proof pins will do), blocking wires (not essential but make life a lot easier) and a tape measure.
Thread the wires through a suitable place in the lace. Shawls often have a nice series of holes along the neck edge, in fact if the pattern doesn't have them I now add them as it makes inserting the wires much easier. The other wires run down the points of this design an the YO holes make it easy to line up those points, the blocking wires mean the points are easy to stretch to the same length. Without wires you pin the points out to the desired stretch. For the neck edge you can thread a length of yarn or fishing wire along the top edge or you can pin it out with a million pins.
After the initial stretch and pin by eye the tape measure helps to finish the job.
Starting at the centre work along the edges pinning as you go, use the tape measure to ensure both sides are symmetrical. Let the yarn stretch a little and you can move the pins out again until you are happy with the dimensions.
Try to get the centre spine to lie straight by smoothing the yarn with your hand and adjusting the pins again. Look at the spacing of the points, are any of them closer to each other than the others? Are they balanced on each side? You can get really obsessive with the tape measure here or you can do it by eye until you are happy. When you wear it no one will notice a millimeter here or there :)
When you are happy with the size and/or fear it will snap if you stretch it any more then you need to leave it to dry. If you can't wait, set a fan to blow across the surface to speed up the drying time. Provided the yarn was damp and you have a good proportion of natural fibres in the yarn, the shawl will block and hold it's shape (a little shrinking back when you take out the wires is to be expected) and will be considerably bigger after blocking. The lace pattern opens up nicely and is revealed in all it's glory.
I love blocking :)
Pre blocking size on this shawl a tiny 34" x 15" during blocking it pins out to 48" x 24". Now we wait ...