Like any other book, you will need to work with an editor to be sure that before you even start submitting queries to publishers, your manuscript is flawless and free of all grammatical errors.
When formatting your manuscript, be sure to research the individual publishers to see what their preferences are on the matter. Some may prefer certain things, others might be strictly against them. The Internet is a great tool to finding publishers for your niche market and researching the submission guidelines for individual joke book publishers.
Once your manuscript is ready to submit and you have selected your desired publisher, it is time to submit a query letter. A query letter is a one-page, single-spaced letter that introduces your book with the intention of hooking an editor in what your book has to offer.
When writing the query letter for your joke book, keep it simple. The old advice for public speaking "open with a joke" may work well in this case, but do not riddle your letter (pun intended) with jokes from your book. Insert just enough to get the attention of your publisher-to-be and let them know what you are capable of. Keep it professional. As funny as your book may be, not everyone is laughing when money is involved.
Illustrations go great with joke books. If you have someone in mind to provide art for your book, mention this in your query letter but do not submit the art with the letter.
Do not fret if the first publisher rejects your book. In fact, this is bound to happen. Instead, keep a list of selected publishers in mind and try again.