Tl;dr: Shuffle a lot using several different methods, then hope for the best but recognize that bad luck happens. Anything that can consistently spread the lands evenly in your deck is cheating.
Part 1: How to change your shuffling
There are several kinds of shuffling, including overhand and riffling styles. Note that each kind has its own weaknesses, e.g. a single riffle shuffle tends to leave the top card of the deck fairly close to the top. In tournament play you have a couple minutes to randomize your deck, so take the time to use multiple kinds of shuffles several times each. Do not use techniques like "mana weaving" that are specifically designed to spread your lands evenly throughout your deck: either you follow the mana weave by sufficient shuffling for randomization, in which case there was no reason to waste the time weaving, or you do not follow it with sufficient shuffling, in which case you're knowingly using an insufficiently randomized deck to gain an advantage, which is Cheating.
Note that even with excellent shuffling your deck will never be "truly" random, but it will be close enough that the next step is:
Part 2: How to change your perspective
After all that shuffling... you still get mana-screwed. What went wrong? The answer is that unlikely events happen all the time if you look with the right perspective. Let's consider just your opening hand, assuming you're playing 24 lands in a 60 card deck. On average, one out of every 46 games your opening seven cards should have no lands. The chance that you get three such awful opening hands in three consecutive games is only one in about a hundred thousand - basically impossible, right? Well actually, there are now around 20 million MtG players. This means that not only have a lot of them seen this phenomenon happen to them, but around 200 unlucky MtG newbies probably had this statistical nightmare happen to them in the first three games they ever played. Think about the apparent contradiction: it's extremely unlikely to happen to you in your entire MtG career, yet it's also virtually certain to happen to hundreds of players right when they first learn the game.
You can probably learn to shuffle a little more effectively, but in the end randomness allows bad stuff - even extremely unlikely bad stuff - to happen all the time.