Increasing in crochet is super straightforward, it simply requires you to do 2 or more stitches into the same space.
Decreasing is a little more complicated than increasing, but it’s still quite simple. It doesn’t require any special skill or any new technique, it’s just a new version of what you already know.
Depending on the stitch you are doing, you will include going into the next stitch as a part of the process.
Double crochet decrease (dec, or dc2tog)
To do a double crochet decrease, you will start your stitch as usual, but before you yarn over and pull through 2, you will insert your hook into the next stitch, yarn over and pull up a loop, leaving you with 3 loops on your hook. You will then yarn over and pull through all 3 loops to complete the stitch.
1) Start as if you are doing a double crochet as usual. But before you yarn over and pull through 2, stop.
2) Insert your hook in the next stitch, yarn over and pull up a loop.
3) Yarn over again and pull through all 3 loops on your hook.
Treble crochet decrease (tr-dec, or tr2tog)
Similar to the dc2tog, you will start your treble as normal, before going into the second stitch to decrease.
1) Start as you usually would a treble crochet. Before the second yarn over, pull through 2, stop.
2) Insert your hook into the next stitch along, yarn over, pull up a loop. Yarn over and pull through 2.
3) Yarn over and pull through the remaining 2 loops on the hook to complete the stitch.