Always warm the fluids. An easy way to do this is to lay it on a heating pad on the low setting for 15 minutes or a seed bag that has been warmed in the microwave. The fluids should be slightly warmer than our skin, about 100 degrees Celsius.
Always use a clean (new) needle. The pink needles are slightly smaller. They will make a smaller hole in the skin but the fluids will go in more slowly. The green needles are slightly larger. They will make a larger hole but the fluids will go in faster.
The higher the bag is hanging above the pet, the faster the fluids will go in. In other words, if the bag is 2 feet above the pet, it will take longer for the fluids to go in than if the bag is hanging 4 feet above.
You can mark the bag with a magic marker to show you where the fluid level is when you start and were it will be when you finish.
When you are done, always pet the animal and offer a treat to make it a positive experience.