Graphic Design is really subjective because everyone likes different things. We always remind our clients that it's important to think of what your target audience will like instead of your personal preference because essentially your advertisements are for them. But for a start, it's good to have something that our client will like (in general) so that the advertisement is appealing to more people. If the client don't like it, there's a lesser chance to appeal to their target audience. It's easy to tell if an advertisement is crafted properly, compared to those that are done haphazardly. Irregardless, your advertisement should be legible at the very least.
Clients should always start with the end design in mind. Nowadays, you can find many references easily online with websites such as Google and Pinterest or if you prefer, choose from our existing designs. It's important for our clients whom we are working for the first time to show us some of the works they like; so that we can gauge the look and feel you're going for. We've encountered some clients that are doing graphic design for the first time who expect "original" designs. We always try to remind them that we are professionals, everything we do is original but inspired by what's going on around us, there's usually no reason to worry about copyright as long as it's done properly. Unless you can find an artwork that's really identical (never happened before), we will then help to rectify the problem. At Jushfoundry, we only work with clients who trust us with our expertise and we are really grateful to have some really awesome clients that are working with us for the long-run; we are seeking more.
As much as we would like to read all our clients's minds, we can't assume what our first-time clients are looking for in graphic design. Our advice is to always reference to an existing design, set it as the benchmark so that your graphic designer know what they are trying to accomplish. The objective is to always get the first artwork done efficiently so that we can save time. After working together for awhile, the style will be set, this is why it's difficult to find a perfect client-designer relationship. Many companies are investing lots of money into marketing because they never know which advertisement will be a hit so it's better to do as many as possible to maintain and increase your market share.