Let the vomiting pass and then hydrate. After you're keeping water down, start a soft diet or a liquid diet until you can stomach heavy food. Feel better.
Are you better now? If you have thrown up and/or had diarrhea excessively compared to how much fluid you can take and hold in or it has been longer than 48 hours and you are still feeling sick, please go to the doctor today!
Also, you/someone for you should report the illness to the place that sold you the crabcakes.
Drink plenty of fluids. If you notice that you start to get tingling in your extremities (hands, feet) then you are dehydrated and need to get some fluids in you. If you can't hold fluids down and have been sick repeatedly for more than 6 hours, then you may think about going to the ER for some IV fluids.
Been there...not fun!