Here's a helpful tip from the Fundraising Fundamentals blog.
The tip is this: Don't clutter your direct mail fundraising piece with secondary calls to action:
... it could also really damage your fundraising results. Putting a bunch of other stuff in your mail package might save you a few bucks, but it will confuse donors and negatively impact your results.
It's true. One of the worst things you can do to a fundraising piece is have more than one call to action.
If you want donors to give, ask them to give.
Don't remind them to come to an upcoming event. Or invite them talk to a planned giving specialist. Or encourage them to buy something.
Just ask them to give. Different calls to action in the same message will kill your results. Every time. I've tested it (many times) and it always happens that way.
The only way you can profit from more than one call to action is when everything is tightly related: You might ask a donor to give a gift and sign the enclosed card that will be given to someone the gift will help. That, in fact, will usually improve response.
But fight the impulse to save a little by adding unrelated material. It's not worth it!