Sometimes it's difficult to find you, even with a GPS. So it's helpful to give more detailed directions or information. This can also be useful for things like where to park or if there is a one way street that Google doesn't know about. Giving this information will help your client get to their appointment on time.
Go to Settings - Location, select the location, then select edit.
Add all the directions and information you need and click done.
You have now added extra directions, remember to save your changes.
Pro tip: Why not add a video, sped up, so that clients can see where to drive and/or walk once they've arrived at your location?