This is a great question and pretty perfect timing, considering Samhain is right around the corner!
If possible, place images of your ancestors on or near your altar and say a prayer to them in the mornings asking for guidance and protection, and again in the evenings thanking them for their guidance and protection.
Keeping fresh fruit or vegetables on your altar are also great ways to honor your ancestors. Once the fruit or vegetables start to decay/rot (usually within a few days) place them outdoors for the animals to eat. The nice thing about doing this is that it requires you to pay attention to your altar.
You can also honor your ancestors by using incense (loose, stick, or cone), feathers, or candles.