The features that you need will vary depending on what kind of form you want to create.
When creating a simple contact form, a very basic form with alphanumeric fields will probably get the job done.  On the other hand, more complex forms may require conditional logic, radio buttons, menu selections, and more.
If you’re shopping for a form builder because you have a form in mind that you’d like to create, take a few minutes to sketch a rough draft of the form on a piece of paper or inside a word processing document.  Get a feel for the information you need, and keep your overall objective in mind.
Once you know what you need to build, check out PandaDoc and a few of the other form builders on our list for a good fit.