Imagine this: you transplant your seedlings from their containers into your soil, which is typical Colorado soil. After a few days you find your plants aren't healthy; they're shocked at being in poor soil and produce carbohydrates disproportionately to proteins; attracting bugs - bugs love carbohydrates.
Seemingly overnight you have a bug problem. So you apply pesticides, which kills the soil life and stresses your plants even more, which causes them to create more carbohydrates. You've killed the bugs (for awhile), yet now your plants don't look so good.
Naturally you think fertilizing might do some good, so you add some (synthetic) fertilizer, which kills more soil life, damages the soil structure, leading to even sicker plants, which attracts more bugs, which require more use of pesticides and fertilizers which kill the very things the soil needs to grow any kind of plant: earthworms and other invertebrates; microorganisms that facilitate the complex symbiotic relationships between soil and plant roots.
Shortly thereafter, your plants die. You are left to wonder what went wrong. Maybe the pesticides didn't work. The fertilizer didn't work. Maybe you just don't have the skill to grow food.
Pesticides and fertilizers are not the answer - vermicompost is. If you let nature do its job, your vermicompost will do its by:
Another common mistake people make is to rototill their garden. Rototilling is a great way to plant seed weeds and rhizomatous weeds (weeds that spread via roots) such as dandelions.
It's a lot of work. Those blades do not go as deep as they need to, which is 2 feet. Instead they grind up the soil about 8" - 10" deep, chop up weed roots, which creates more weeds, and plants weed seeds fairly deep, which weeds seem to thrive on. It seeds those chopped up roots down deep which makes pulling them even harder and guarantees the spread of more weeds. With dandelions, bindweed and some others, even the tiniest root segment down below will grow into a full-fledged weed and fast.
The best way to prep your garden bed is to double dig with a spading fork. It's easier on your back, digs deeper than other shovels, loosens the second, deeper layer than needs it most and make double digging a joy. Google double digging technique for the whys, hows and whens.