Check your fingernails and toenails for discolored stripes that extend from the cuticle down toward the tip. This is one of the go to signs for subungal carcinoma, a form of skin cancer. This can also occur with normal bruising, which is why you shouldn't panic, but should see a physician.

Yellowing of the whites of the eyes can indicate liver damage, this is a form of jaundice.

If your breath smells has a sweet/acetone type odor or your urine attracts ants/bees (if you happen to urinate outside, like when camping) you very well could have or are developing diabetes.

If you have right shoulder/shoulderblade pain that gets worse after eating you may have a problem with your gall bladder (the nerve that goes to the gall bladder passes by your right shoulder and if irritated makes your brain think the pain is there rather than near the stomach).

Stroke like symptoms are not worth any risk and you should immediately go to the ER. However, for personal ease of mind if you develop one-sided facial paralysis you can (after calling 911) try raising your eyebrows while looking in a mirror. If they both raise up - you're having a stroke. If only one side raises up and the other is paralyzed, you almost certainly have Bell's Palsy, which is not a stroke, is mostly benign, generally goes away on its own but can be treated sometimes with medication. It's cause by inflammation of the facial nerve as it exits the skull near your ear rather than damage to the brain. Again, don't risk it call 911, but it can bring some mental relief.

Unequal pupils are grounds for 911. Sometimes it's benign, but it's also sometimes an indication of a brain bleed.

Anxiety causes you to breathe quickly, which causes you to lose carbon dioxide too quickly, which causes your blood pH to change. Without getting too technical, this results in tingling sensations at your fingers, toes, and face. This will probably make you more anxious and breathe faster, making the problem worse. Breathing into a bag really helps this, as you breathe that CO2 back in. Also knowing this will let you know that this sensation is normal and that you are not dying, perhaps alleviating some of the anxiety. Just a couple things we look for.

There are volumes and volumes of books dedicated to signs and symptoms of diseases, as you might guess. Pretty neat stuff.

-ER EMT going to medical school