This website gives a nice run through on forms, including why they are important and how to use them. It also gives advice on how to design them based on the user's perspective, instead of the database's. It highlights the need for forms to be easy to use and to keep the time required to fill them out as short as necessary. One important detail that is mentioned is how important protecting data is, so that if a user accidentally exits a page while completing a form, they can return and their data won't be lost. It also discusses conversational form of text input, which is turning a form into more of a conversation. I have seen this style used more and more in apps that I use and prefer it over regular forms as it is more interactive.
This website focuses on the same types of information as the first website, but is specialized for mobile websites and devices. I believe this makes it extremely valuable, as there is an increased amount of users who access websites from mobile devices these day. One key aspect that I noticed was how mobile forms should be as minimal as possible, as there is less screen space to work with. Don't duplicate fields and also avoid dropdown menus, as those might be too large for a phone screen. It also suggested using placeholder text to show users what is expected, which saves space as the description is no longer needed outside of the input box.