Hopefully you never have to administer first aid for your dog, but if you do, you want to make sure that you have a complete kit.
Top things to include:
1. Clean cloth's for applying pressure to any injuries.
2. A copy of your pets medical and vaccination records. In case of having to run to an emergency vet, having this papers close at hand will help the vet know if your pup has any allergies, and what vaccinations they have.
3. Digital Thermometer for testing their temperature. Remember that dogs temperatures are taken rectally not orally. When cleaning it never run it under water, as this can ruin it.
4. Gauze for bandaging wounds. Remember not to remove old layers. Always stack! New gauze goes on top of old gauze, or else you'll remove the scab that was being formed.
5. Adhesive tape for securing the gauze.
6. Liquid benedryl. Sometimes benerdyl can mean the difference between your dog being able to breath, or not. With this make sure to also pack needless syringes to administer.