Build the first version of the landing page, and then start testing it, changing one element at a time. Change the position of your headline for a few days, and then evaluate the results. Change the color of your call to action buttons for a few days, and then evaluate the results. This type of testing is usually referred to as A/B split testing, and is a key instrument when it comes to conversion rate optimization.
It is also recommended to segregate your audience. If you send everybody to the same landing page, it is unlikely that you are going to experience all of the benefits that your PPC campaign has to offer. When you design landing pages which are specific to the keywords and ads that you are using, you can then send people to pages which are specific to what they were searching for. That can really make a difference when it comes to boosting conversion rates.
Finally, designing the perfect PPC landing page will allow you to gather the data that is necessary to drive your business to the next level. The information can show your website's bounce rate, the age of your visitors, the type of devices that they were using when they visited your website, and much more. Typically, you will use Google Search Console in conjunction with Google Analytics to get access to this detailed information. There are several third-party services that can give you access to some of this data as well.
Be sure to pick a relevant URL for your landing page. It's one of the first elements that your visitors see when your ad is displayed in from of their eyes. Google makes it easy to hide a longer URL, allowing you to use something like YourSite.com/YourProductName. So, choose a good virtual URL for your landing page.
Ad text is important as well, of course. It's best to let a specialist write the ad copy for you, or at least learn from your biggest competitors, who have already done their homework. Don't forget that even great copy needs to be refreshed every now and then.
It is crucial to test and optimize your landing pages regularly. Your competitors are already doing this, and you don't want to miss on the opportunity of getting more customers.