There are many different breathing techniques.
Some of my student's favorites are the following:
*Hot Chocolate Breathing: Close your eyes and picture yourself holding a cup of your favorite Hot Chocolate (mine would have mini marshmallows and a peppermint stick in it!). Then as you hold your cup you take a deep breath in to smell the delicious scent of your Hot Chocolate. You can't wait to take your first sip, but it's far too hot! You need to cool it down by blowing gently so that your Hot Chocolate doesn't spill out.
*Breathing Buddy: Laying down in a cozy spot with a stuffed animal friend (or something similar) you place the Buddy on your belly. Take a nice deep breath and blow it out while balancing your Buddy and doing your best to make sure they don't fall off.
The app Calm has released these free resources for you to use whether or not you have the app downloaded. Try this out and see if it is a strategy for you!