Landscaping a hill can be a bit of a challenge. You can hire a landscaping company, but that can be expensive. So here are a few ideas if you're a DIY kind of person.
The first thing to consider is water drainage. If you are landscaping a hill, chances are, you will be rerouting the flow of water. Make sure you can direct the water to a safe place (not your neighbor's yard!) If you don't have a clue about this, I would hire a landscaper so you don't have problems.
1. Build terraces on steep slopes using railroad ties or large flat rocks (the ones used for landscaping). Don't use railroad ties around edible plants because the ties might contain creosote. The ties/rocks will mark the edges. Then use soil to create level spaces for planting.
2. Guide the runoff water to appropriate places through the placement of your railroad ties/rocks.
3. Spread mulch between the terraced steps to protect the soil.
4. Select plants. Creeping plants like periwinkle, ivy, and creeping juniper work well. At the bottom half, use shrubs to help prevent erosion. Japanese yew, day lilies, and hostas are good choices. At the bottom, have flood-tolerant ornamental grasses and trees.
5. Embed medium sized boulders in the bottom half to add visual interest. Don't just plop them down, though, or they'll end up rolling. Bury the stones to a third of their height and pack dirt around the base.
Other things you can do, are cover the bottom half of the slope with landscape fabric (cut holes for trees and shrubs), to reduce weeds. If you want, rather than covering the fabric with dirt, you can cover it with a four inch layer of pea gravel. The gravel creates an interesting visual effect for the slope. You can also add steps. Retaining walls at the base are another possibility, but I would leave that job to the pros. With careful planning, you can create a beautiful landscape for your slopes.