A quick-release knot is generally used for tying in most cases. A quick-release knot can be tight and secure but easily pulled to release in case of an emergency.
You need to decide if you want your horse still there when you come back. If you tie so it can get loose, you are teaching it a very bad habit of pulling back to get loose. This can be very hard to correct. Tie your horse so that it cannot get loose, and teach it to stand tied so even if something scares it, it will not pull back.
To learn more about knot tying as it relates to horses, please review our instructional video series.
