I would suggest walking the trail before going after gaits if you do not know the trail well. There could be rocks or pot hole your house could step on/in that can cause serious injury and tripping.
I would also suggest putting polos or support boots on your horse for extra tendon and ankle support. This can also prevent cuts or exposure to plants that can cause rashes on your horses lets.
Always be aware of situations your horse could spook wether it be animals jumping in front of you, animals making new noises your horse could spook at, other horses riding the trial that bite at your horse or try to kick and know his reaction.
I would suggest bringing a lead rope and halter if you fall off your horse and can on get back on or do not want to, you can lead him with that instead of his rains and pulling on his but more than needing to.
My friend had put a dog tag with her phone number on the d ring of her saddle and bridle when trail riding so that if she fell off her horse and he spooked, if someone found him they can contact you.
I would say don't go too fast on dangerous terrains!
And be careful with horses that you don't know! Any horse can kick and one should always be aware of this. Many have broken legs as a result. Do not approach the horse in front of you too closely whether it is a known kicker or not :)