Stir with a wooden spoon.
Don't scrape the sides, this can cause sugar crystals to end up in your caramel, making it crunchy instead of smooth when done.
Once you insert your candy thermometer, don't move it around or remove it and put it back in, as this too can lead to sugar crystals.
Heat on medium, if too high, you will see brown specks, which is your candy scorching; if this happens remove immediately from heat, and turn down, then return.
When cutting and packaging, it helps to set the pan on a tray with ice cubes to keep cold, making handling much easier.