If you have a lot of food, then it's a good idea to make sure that it's all together in one place (i.e. in the same suitcase and easily accessible) so that if you are asked to show it to them, it's easy to find it. There's nothing worse than having to unpack ALL of your luggage trying to find something, and then having to hastily repack it all when your tired and trying to avoid creasing your shirts....
If you're bringing loads of food, I would recommend writing out a list of exactly what food you have before you leave. This saves trying to remember it all when questioned by customs officers.
When I last passed through MCO, we were headed to WDW and then visiting relatives, so we had brought them all sorts of British food (mostly crisps and chocolate). We made a full list of all the items and quantities, which we just showed the customs officers. I'm pretty sure it helped, and it made the process much smoother and easier. We had almost an entire suitcase of food and were not asked to open our cases. Declaring food doesn't automatically mean they will search your cases.
As others have said, always declare everything. It's a very good idea to research what's allowed and not allowed in advance. However, the system works on the principle that it doesn't matter whether you think it's allowed or not - that's for customs officers to decide, and that's why they ask you to declare food. If you declare, then the worst that can happen is they take the food off you, and tell you to have a nice day. If you don't declare it, then you have lied on a legal document, and therefore are deemed to have intentionally deceived customs officers, and they may take action regardless of whether or not your food is OK to bring into the country.
I've seen enough fly-on-the wall customs programmes on TV (the more obscure sky channels) to know that it's always better to declare. The rule that the Aussies use in those programmes is that if it goes in your mouth, it's food. I'm not sure that's always true(!) but I think that's a good guideline.