I have been working a lot with forms lately, and thanks to my favorite client (they will recognize themselves) I also learned a ton! Here are my key takeaways around forms.
If you need to ask for a list of things, like diplomas for an application form, then start by asking about their first diploma and include a question “Do you have another diploma?” and branch the “yes” answer to a new set of questions and so on.
Each question is given back with the answer inside the task as a result of a submission. But the question description isn’t so make sure your team does not need to see the description along with the answer to make sense of the data.
I am a big fan of emojis and I believe they make a form cool and fun to use. Place an emoji in front of the questions. Be careful though to not offend people: an old man for a question about age or a man (not along with a woman) for a question about gender might be a bad idea.
I reached the limit of the branching mechanism and the magic number is 5: you can’t nest more than 5 branches.
The biggest form I created so far had 120 questions, no technical limit in sight!
Make sure to connect questions to existing custom fields if you want to sort submissions based on that value later, or filter, or just export the submissions as a CSV and have the freedom to do whatever you want.
(NO LONGER TRUE) You can’t connect a “multi-select” question to a drop-down custom field. If you need to ask for several values, one solution could be to use a drop-down question with a “Multiple values” option that shows a text field for free input.
If you need to have an “I agree” or “I understand” checkbox, you can use a multi-select question with only one option. And make it required.
If you need to ask for a number and a currency, you don’t have much choice: ask for the currency in a drop-down, or ask for the whole value in a text field.
For your information, if the field you connected to the title of the task (using “Select a field for task titles”) is left blank, the name of the project will be used.
Bonus: most forms include “big” sections with explanations like “Part II: personal data. bla bla bla”. You can’t create sections in a form, but you can have a question of type 
it doesn’t appear when view the form. Is there a work-around?