Curb appeal is a "pre-marketing" attention to detail item. It is extremely important. I've had Buyers "skip" homes based on the exterior - fearing what they may see inside.
Here are some quick and inexpensive ideas to help you along your way:
1. Trim - Trees high enough to be able to walk under. Bushes and plants to an intentional and deliberate shape.
2. Lawn - Mow to a lush-looking length - not so low it's barely visible.
3. Flower Beds - Plant those in season. Colors to compliment your house.
4. Planters - Fill with flowers or plants. Remove if not in use.
5. Wood Trim - Paint if necessary
6. Driveway & Entry - Swept clean.
7. Exterior Lighting - Replace nonworking bulbs, remembering those in landscaping.
Hope this helps.