When determining the temperature to cook your meat to, there's a crucial distinction to be made between whole muscle cuts and ground meat. The food scientist Harold McGee explains:

“… meats inevitably harbor bacteria, and it takes temperatures of 160 degrees Fahrenheit or higher to guarantee the rapid destruction of the bacteria that can cause human disease — temperatures at which meat is well-done and has lost much of its moisture. So is eating juicy, pink-red meat risky? Not if the cut is an intact piece of healthy muscle tissue, a steak or chop, and its surface has been thoroughly cooked: bacteria are on the meat surfaces, not inside. ”

In other words, with whole cuts of meat it is the external temp, not the internal temp, that must exceed 160 degrees Fahrenheit. Normal cooking methods — sauteing, grilling, roasting, braising, etc. — raise surface temperatures far above 160 degrees Fahrenheit. (To get a sense of this, consider that meat only begins to brown at 230 degrees Fahrenheit.) People very rarely get sick from rare or medium-rare meat. Overwhelmingly, people get sick from the way meat is handled in the home: from cross-contamination, lack of cleanliness and holding meat at dangerous temps. Internal temperature should be the least of your worries. more

Lightly touch thumb to finger on same hand. Feel the fleshy base of the thumb with the other hand. That's the same feel the meat will have.

Seafood cooks quickly and is usually thin. This means that it can be tough to measure with a thermometer, so use the visual indications.