Dogs want your attention. If they jump on you and they get attention, negative or positive attention is their goal. Dogs like food, so if snatching something off the counter always results in a treat, then that behavior will also most likely continue. Your dog is not going to know how you would prefer them to act unless you teach and guide them.
- There are many ways to stop your dog from jumping on you. The way I prefer is to teach a solid sit and sit stay. If you train this well, that means your dog's front feet stay on the floor. If the dog approaches me and looks like they are going to jump, a well trained "sit" will stop them in their tracks. There are many steps to a well trained sit, especially off leash and in the house. If I keep telling them to sit as they approach me, they learn that this is how I want them to approach me. Also be sure you are in fact giving your dog an amount of attention every day and spending quality time with them.
- The dog food snatcher is another story. You should always be around to supervise food that is out, unless you have really put some serious work into this. Commands like "leave it" that are trained correctly and thoroughly (before they reach the food) are effective. I usually start with stay commands around the food. My favorite stay command is the place command, where the dog can be comfortable for awhile as the food is prepared or left out. The "let's go" command can also stop an approach to the food with coming towards you instead.
There are many ways and commands that can help you guide your dog to more acceptable habits and responses. The dog owner just needs to teach and guide their dogs there.