1. To decrease double crochet stitches, y/o, insert hook, and draw up a loop. You have 3 loops on your hook:
2. y/o and draw yarn through two loops only. You now have 2 loops on your hook:
3. y/o and insert hook into the next st and draw up a loop. You now have 4 loops on your hook:
4. y/o and pull yarn through two loops, leaving you with 3 loops on your hook:
5. y/o and pull yarn through the remaining 3 loops:
Done! This is what 4 in a row looks like: