Keep a record of what you have planted or better yet, keep the labels that came with your plants. This will help answer any questions about what the plant may need if it starts looking poorly and will remind you next year of what you liked and what didn't work. It also helps to take pictures and label them. You'll remember color combinations and favorite plants.
If you start a garden journal, you can also record how plants perform, when flowers are in bloom, how large a harvest was and all kinds of information that will help youmake a better garden next year.