A green thumb? I used to have one, when I was a rookie gardener! Now, I wear gloves. 
As a gardening veteran, I will share my personal joys of developing the proverbial green thumb. It’s a literal term, and at least half the fun is getting your fingers (and your thumbs!) into the fray of grit, goo, and greenery.
Now, there are gardeners and there are yard servants – the latter toil in the soil, while gardeners get to ENJOY their labor of love. How does one go from yard servant to gardening savant? Expertise is derived from trial and error. Here are some trials, and my errors:
Tools Rule
My good intentions could have paved the road to Purgatory, but I didn’t quite have the necessary inventions. What’s the ol’ adage about planning? Prior Planning and Preparation Prevents Poor Performance! These Six Ps of Planning sure would have helped back then!
Location, Location, Location
Plants are like businesses, because location is their key to success! Location doesn’t simply mean “in the ground”; it means a myriad of considerations, such as soil, moisture, sunlight, temperature, competing interests, insects, and animal or human propensities to disrupt the greenery’s harmony.
Imagine my dismay after watching several pricey greenhouse items dwindle to brown sticks or lifeless figures of seemingly wanton neglect. I am innocent, Your Honor!
Research
Research? They’re plants, not rockets or brains! Still, live beings require a balance of earth, wind, and (acro)spire! I unwittingly planted an Autumn Clematis vine on the north side of my home, which has spawned a bazillion clones, all of which seek to cover my house with tenacious ropes of climbing zeal!
Establish your goal
A clear aim helps you hit your target. Ask yourself what you want to see in five or ten years. Assuming you properly planted healthy, motivated cultivars, you may expect them to flourish and fill in the garden spaces.
Don’t assume the healthy, motivated sapling Dwarf White Pines were marked correctly on their tags! My would-be five-to-seven-feet pine trees are now hovering at a quaint sixty feet. White Pines double their height every year, so I am positive my neighbor curses me every time the wind blows!
Don’t expect miracles
Successful gardening has many variables. Set reasonable goals. Remember that Nature has a way of taking care of her own. It’s just a sign of the thymes!