The best practice is simply to breathe as you would normally and not try to do anything specific. There are some fancy pants breathing techniques out there that are useful, and I do think you should try them at some point.  But for the purpose of getting started and getting established, just breath like you would normally and don't try to make it faster or slower or hold your breath, etc. etc. You will find that as you relax, your breathing will get more comfortable and slow down naturally. It's not an objective, it's an outcome.