Start with the imprint text
Write down exactly what should appear on the stamp. For a company this may include its name, address, tax number, phone or email, depending on the purpose.
Use a good-quality logo
A tiny image taken from a screenshot may not reproduce well as an imprint. Bring the vector file or the largest original you have.
Think about the size
More text needs more surface. If the stamp must fit a specific form field, mention that before the layout is prepared.
An old stamp can be a useful reference
If the new one should keep a similar layout, bring the old stamp or a clear impression of it.