Cast On for Centre-Out Knitting: Emily Ocker's Cast On
I first saw this cast on described in Elizabeth Zimmermann’s Knitter’s Almanac. It's a great cast on for beginning knitting at the centre and then working in the round, out in all directions, e.g. pillows, blanket squares, medallions and baby blankets. 
 
Once the desired number of stitches has been cast on, divide the stitches onto double pointed needles or a circular needle, gently pull the tail yarn to close the centre hole and bring the stitches closer together; proceed with the pattern. When finishing, pull the tail yarn snugly to totally close the hole at the centre. Weave in the yarn tail.

Step 1
Loop yarn with end attached to skein lying on top of tail end
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Step 2
Take crochet hook through loop and catch yarn
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Step 3
Pull yarn through loop
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Step 4
Catch yarn above loop …
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Step 5
… and pull through loop on crochet hook to complete a single crochet
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Repeat Steps 2, 3, 4 and 5 until until desired number of stitches has been cast on.
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Repeat Step 2.
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Repeat Step 3.
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Repeat Step 4.
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Repeat Step 5.