Like tuna1957 said, check out all the tutorials, but don't jump right into the more advanced ones, they might confuse and discourage you until you've studied some of the ones aimed more at the beginner level. Work your way up. And as far as the YouTube videos, while there are a lot of them that do take the time to explain how to do certain things, there are also a good number of them that just speed through the process, with no attempt whatsoever to explain what they are doing or how they are doing it. I call these the "Wow, ain't I impressive" videos, and while they can be entertaining they offer no value as a learning tool for the beginner.
The way I learned was to pick a model from the warehouse and try to modify it. Just keep at it and you will learn a lot. I did this with several warehouse models before I attempted to create anything of my own, and I learned so much in the process.
And most importantly, do take advantage of the forums here. Take the time to just browse through them and you'll be surprised how much you'll learn. And ask questions! There are so many incredibly helpful people here who are willing to take the time to explain anything that you have questions about. Just remember that even the most skilled modeller here started out at the level you're at right now. I know I wouldn't have gotten very far without their willingness to answer even my "dumbest" questions without talking down to me or making me feel like I'll never learn how to do the amazing stuff that they do.
Trust me, if I can learn (at least some of) this stuff, anyone can.
Looking forward to seeing more of your work here as you progress.
Oh, and figure out which plugins might be of help to you and learn how to use them. If you can't figure out how to do something, see if you can find a plugin that will help you do it. Even if you can't find one, don't assume there isn't one. Post a question here on the forums about it, and you might be surprised. But don't overdo it with the plugins at first, you'll just overwhelm yourself. There are some that are best left for later as your skills grow. The sheer number of plugins available can be daunting, I know it scared the crap out of me. Maybe somebody here can make a list of the plugins recommended for those just starting out with Sketchup, and which ones to add as they reach certain skill levels. They make everything so much easier now than it used to be.
Wow, time to get down off my Sunday morning soapbox, grab my laptop and head out for some coffee.