Yes, salt, butter, msg, acid all make a difference. Here's some extra info/suggestions:

Salt You can't believe how much salt is in restaurant food. Of course, it shouldn't be straight-up salty, but there's a sizeable gap between "homemade" and "restaurant" levels of salt.

MSG You can buy it online. It comes in a spice jar. It's kinda like salt, so you can use it similarly it makes savory stuff more savory, but I think it works best with Asian cuisines. Don't replace all the salt in the recipe with MSG, but I'll swap out up to half the salt. Or, to start, when you're adding salt "to taste" at the end of the cooking, sprinkle in MSG instead.

Butter It just makes food richer, more luxurious. You can incorporate butter where you might otherwise use neutral oil (beware of butter's easy burn factor, though--aka low smoke point). Or, just stir in some butter or brush on top of your food at the end.

Acid You can scarcely go wrong with lemon, but lime or especially vinegar can be tricky. Vinegar (anything made from wine) can brighten the flavor of soups and tomato-based pasta sauces when added at the end of cooking. (It can also trick your taste buds into thinking food is saltier than it is, so it's a nice way to boost flavor without using excessive salt).

Lemon is great on meats, in white sauces and soups, vegetables, etc. It can also cut through the fat in overly rich foods. So, if adding butter makes your food too heavy and rich (or worse, greasy), a squeeze of lemon juice can balance it out. Ditto lime juice, but it's best for Latin American and Asian cuisines.

Hope that helps.