Several rules for healthy work with large and medium clients. Don't be afraid to follow them, so you can sleep peacefully.
Work begins only after a 50% advance payment is made. This includes the first stage (sketching, presenting directions). After approval of the concept, the client pays the remaining amount and the designer finishes the final version of the project.
All amounts are non-refundable.
It's better to immediately establish a percentage for delayed comments for complex and large clients. It's enough to give a window of 1–2 weeks to provide feedback on the concept. The final amount of the project increases for each day beyond the deadline.
The argument is simple enough: you have your own project planning. To deliver work on time, you need to stay within this timeline. You don't want the project to drag on for years, popping up in the middle of other work.
For the client, this is motivation to respect your time. Avoid friendly agreements and "putting yourself in their shoes", because this is a trap that will result in you being penalized.
Set an acceptable number of concepts for you, and then the number of revisions for the chosen concept. I work in a 3/2 mode. All designer games should be paid as separate work.
Set a range of new requirements that may arise from the client during concept development. This may include a list of merchandise, graphic units, logo variations. Everything that is added beyond or significantly changes the work on the concept should be paid for separately.
Raise the question in advance about the formats and programs in which the client needs to receive the result. It's not cool to find out at the end of the project that you used InDesign, but the client needs everything in Illustrator.
Find out if the client has a design team for further support of your project. Talk to them, it's always useful.
Don't start work until the entire scope of work is documented. Don't accept the wording "a set of office supplies", instead, itemize exactly what accessories need to be designed. Each icon, pen or business card should be listed on a separate line.
Separate the set that needs to be transferred to the client in the form of source or print files. Everything else is given by default in a demonstration JPEG.
At the end of the project, always demand a letter or document that confirms the completion of the project from the client. Contact the manager, accountant, financial director, and cleaner until you get this document.