Newbie Mistake #4: Growing too few plants. And:
Newbie Mistake #5: Growing too few varieties.
I'm not saying turn your whole house into a pot farm. But for a given fixed space -- like my 2x4 tent -- more plants is better. And when you're just starting, so is more types of plants.
I have two plants in my tent, now in 7 gallon cloth containers. My idea was that I'd grow 3 or 4 foot plants (dumb idea -- I'll say it again: vertical growth is a waste), and they'd each fill out roughly 2ft x 2ft of area. Which is fine, and I expect I can do it. But 3 plants, or 4 plants, or 6 plants could fill out the same space much faster, and I'd be harvesting the same amount much sooner. The only savings is a few seeds, which are not cheap, but neither is my time (which, reincarnationists notwithstanding, I assume I don't get back -- ever). And once I get in the groove I'll be cloning, making the seed cost a non-issue.
As clearly as I can say it: More plants yield a quicker harvest. And the sooner you harvest, the sooner you can start your next grow, which in the end means more weed. Period.
As far as varieties, I purposely grew only one, reasoning that different varieties would grow at different rates, need different amounts of flowering time, etc. And I figured the slower growing ones would be farther from the lights, so grow even slower, get even farther behind, and it would just get worse and worse. Idiot: You raise the smaller plants up on a pile of books or something, so that they're all at the same height. And if they're not ready to harvest at precisely the same time, then you harvest them as they come ready, not such a big deal. (You don't rush any of them, though -- that's a newbie mistake I plan to avoid. I want my weed mellow.) Meanwhile you get more experience by seeing how the different strains react to whatever you're doing, you're less likely to wipe out your whole crop with one bonehead maneuver (some of the strains will probably tough it out), and most importantly (and obviously), you end up with a variety. Which is important so you can figure out what strain or strains you like best, and focus on them in the future.
I'm almost ready to add "Spending all my damn time on the forum instead of paying attention to my plants" as my next Newbie Mistake; in the interest of dodging that one, I'll give it up for now. I'm sure I'll be making more mistakes soon, and will return to fess up when I do.