Most foods contain naturally-occurring sodium. Fresh foods have less than canned or prepared foods, but you will find it everywhere. Our bodies need sodium to support life. However, most people in the U.S. consume far more than the amount needed to stay alive. People need 200-500mg (milligrams) per day.  The average U.S. diet contains more than 3500mg of sodium. Most people have few problems with sodium intake. However, as in almost everything, the problems happen at the extremes. According to the Centers for Disease Control and Prevention, 2300mg of sodium is the maximum recommended daily amount for most people age 2-50. People who are 50 years and older and African-Americans of any age should limit their intake to 1500mg per day. Additionally, anyone with high blood pressure, diabetes, or chronic kidney disease should follow the same guidelines.
Why Worry About This?
Sodium aids in the absorption of water and nutrients. Chemically, all table salts are sodium chloride, and when broken down, the chloride forms part of hydrochloric acid (stomach acid). It also keeps the correct amount of water inside the blood vessels. Too much or too little sodium results in many problems. 
A low sodium diet rarely leads to low sodium levels in the blood (hyponatremia). Extreme water intake, excessive sweating, vomiting and diarrhea, and some medications are the cause of hyponatremia. Common side effects noted with mild hyponatremia include muscle cramps, headaches, nausea, fatigue, and confusion. Severe cases can cause brain swelling and death although this is very uncommon. 
When there is too much sodium in the blood (hypernatremia) other conditions are much more common. Excess dietary sodium can elevate a person’s blood pressure.  Salt can pull calcium from bones, increasing the risk of osteoporosis.  It also prevents the kidneys from properly excreting excess water, which can raise blood pressure.  Some studies suggest that high salt diets increase the risk of kidney stones possibly due to the excess calcium from bone loss. 
What Does Salt Do?
In ancient times, salt was a form of money and it was one of the first food preservatives. While still used as a preservative, we most commonly use salt to season food. How does salt make food taste better? Saltiness is one of the five taste sensations, the others being sweet, sour, bitter and savory (umami.) In foods, it can hide off-flavors and make food feel thicker. It also enhances sweetness. (Consider sea salt topped chocolates, or the salty-sweet kettle corn as exemplars of this combination.) Salt will mask bitterness in foods. This is why sometimes people add a pinch of salt to the coffee grounds before brewing. 
What Alternatives Are Available?
If you want to enjoy a low sodium diet, you will need to be patient and find substitute flavors. Anyone who enjoys food with “normal” levels of salt will find low-sodium versions to be flat, and have less flavor. Our taste buds become accustomed to salt levels and any reductions make food taste bad.  In reality, with less sodium in the food, you are actually tasting the food in its natural state. Teaching your taste buds to appreciate that new level of flavor takes a little time, but it will happen.
To reach a low sodium lifestyle, you will need to stop eating prepared food. This includes most canned foods, prepared frozen meals and everything in your local delicatessen. Food labels in your grocery store will help you make healthier choices.
Restaurants will pose a challenge. For example, eating a Quarter-Pounder with Cheese at McDonalds will add 1100mg to your daily total. A medium French fry adds another 190 mg.  Panera Breads offers food choices that appear healthy. Ordering a Roast Turkey, Apple, and Cheddar sandwich will add 1260mg of sodium to your daily total.  An appetizer portion of calamari at Olive Garden has 2400 mg. Finishing your meal with Chicken Parmigiana (2980 mg) and two breadsticks (920mg), will give you a total of 6340mg for a single meal.  If you choose menu items that have the fewest sauces and toppings, you are more likely to eat healthier (both with less sodium and fewer calories.)
Specialty salts, like Himalayan Pink, kosher or Celtic Gray are not substitutes. When searching for salt substitutes, you can choose between non-sodium salts (usually potassium chloride) and other flavoring agents. Potassium salts will provide a salty character, but when used exclusively they also give a bitter, metallic taste. Additionally, people with underlying kidney problems and some heart conditions cannot use potassium salts or risk worsening their diseases.  Unless you are healthy, I cannot recommend the use of potassium as a replacement.
When you move beyond the replacement salts, you find a wide range of flavor enhancers. In the low-salt kitchen, spices and herbs will be your friend. Leafy herbs like cilantro, basil, rosemary and oregano will help open the flavor ranges of your foods. Ground seeds like mustard, celery, dill, and peppercorns will add a punch to the flavors and aromas. Savory vegetables like onions, garlic and chiles will also bring additional flavors to many foods.
There are options that move beyond simple spices and herbs. Consider adding an acid to the food, like a specialty vinegar, or the juice of a lemon, lime, or blood orange. Acids tend to lighten and brighten other flavors. Other liquids, such as beer, wine or spirits will do the same. Adding fats to a dish will also provide a similar thickness to the finished product. Try different fats for new effects, like duck fat, or a small amount of bacon fat.
Use foods with umami carefully. Many umami-rich foods are also sodium rich, such as soy sauce, fish sauce, and anchovies. Instead, try adding tomato paste, mushrooms, and matcha (green tea powder.)  Also, substitute some lean cuts of meat with types that are fattier. Cook a chicken thigh with the skin on and remove the skin before eating. This is as low fat as cooking a skinless thigh but has much more flavor.
Learn new cooking techniques. Cooking your meat over very high heat and searing the outside will create new flavor compounds through the Maillard reaction (the technical term for “browning”.)  Commercially smoked meats often contain high levels of sodium, but home-smoking your meat, poultry and fish will create delicious foods with no added sodium. When you caramelize your vegetable over the grill, on the stove, or in the oven, you enhance their natural sweetness.
Lastly, if you drink alcohol, try different wines and beers with your meals. Similar to using them as ingredients, sipping an alcoholic beverage while eating will enhance the food’s flavor. Try new wines with your dishes. All wines, sweet, dry, red, white or blush, will interact with your foods to create different flavor profiles.
Living with a low sodium diet is not the end of tasty foods. Like with any change, give yourself time to adapt to your new choices. Explore new flavor combinations and use spices, herbs, and other flavoring agents liberally.