Lots of fresh herbs, I have chives and parsley on hand constantly and add them to everything lol. You'd be surprised how tasty steamed rice is if you add a little lemon juice and a few herbs. I add olive oil or butter too but I'm not scared of adding fat to my food. Fresh garlic adds lots of flavor too. Lots of spices too like cumin, coriander, allspice, nutmeg, chinese 5spice, etc.
Roasting brings out a lot of flavor in vegetables. I like to roast vegetables for everything! Steamed veggies have their place but I choose the roasted ones any day.
I also add frozen peas to just about everyting - salads, stir fries, pasta dishes, rice dishes, and they hardly need any cooking at all, just throw them in at the end and they thaw immediately in the food.
I've learned to crave color in my food - the more colorful it is the more flavorful it is.