Illustration contracts don’t have to be complicated. Most of the time your client will send you a contract to sign, but for every other project, you need to protect yourself against clients that might take advantage of you.
You always want to have a written (email) record of what you have agreed with your client. If any problems arise later in the process you can refer back to the agreement to resolve any disputes.
Ask your client to agree to your terms by email.
Getting an outside perspective on your portfolio can vastly improve your work. By seeking out the opinion of someone in the industry, you can get a fresh pair of eyes on your work and they can often see what you can’t.