Consider the amount of stuff that's going on, in the game. A player should not have to read ten cards, twenty tiles, and thirty board spaces, in order to understand what's going on.
Try to keep visible information to a minimum.
In some complex games, working out what's going on is half the mental challenge. I want the challenge to be the strategy, not comprehending the game.
I once played a Magic knockoff. I drew my first hand of seven cards, and each card had many lines of text. Amongst those many lines of text was even more complexity, as there were jargon words in there, that weren't self-explanatory. Not only this, but the game was cooperative. I needed to read and understand not just the cards in my own hand, but those in the hands of all my teammates as well.
Caverna has a large number of board spaces that players can go to. These are mostly self-explanatory. In addition to this, however, there are 48 building tiles laid out. Better read all of them right at the start of the game, so you don't miss something! Don't worry though, by your 10th-20th game, you'll have a good grasp of these tiles. There's even a handy "introductory game", with only 27 tiles visible.
Information is much more acceptable when it builds up over time, however.
There's also an "ugh" factor, that puts people off, the moment they see the game. If a game looks complicated, people will be less likely to want to play it. And, if it's too late for them to get away, it's feelbadness, before the game has even begun.
A simpler game also just looks nicer.
In my gangster game, I kept increasing the number of location cards on the table, and eventually there were twenty. I needed to do this for gameplay reasons, but it was a serious information overload problem. I decided that the top and bottom five locations would be the same every game. That doesn't help with the first game, but it does afterwards. I colour-coded all location cards by function. I redesigned all locations to be simpler. No location could have more than two icons, or more than one line of text.
Use a few icons. Half of what your game is communicating should be done with icons, not text.
Even then, your game shouldn't be covered in icons.
Cards should be simplified, and the player should have the least number of them possible. Eliminate text.
Group similar pieces of information together.
A Feast for Odin has 61 different actions a player can take on their turn. However, rows of actions are clumped together, with a label like "Crafting" or "Hunting" next to them.