Reddit mentions of Practiceopedia: The Big Book of Practice Help

The main mistake people make is: "I'll just teach myself".
Don't. You'll get so far and get stuck and have no idea why you're stuck.
Get a teacher.
You'll get from A to B faster and when you get stuck someone will explain to you why you're stuck and what you need to do to correct it.

As far as specific common technical errors goes there are a couple of decent videos here:

https://www.youtube.com/watch?v=kPBqjgF9-l8
https://www.youtube.com/watch?v=qs4Oo3R3GVQ

Another common problem beginners make is that they don't know how to practice. To a lot of people "practice" means "I'll pick my guitar up and play it for a bit". OTOH good quality practice is planned and it has a point (learn a new piece efficiently, improve your technique, hone your musical interpretation) - it's not just noodling around.

Practice planning doesn't have to involve the ludicrous Tom Hess version of planning which is something like "You will have a five-year goal and then work backwards and work out all the steps to achieve that goal in minute detail". If you try and do that you'll spend more time planning than you will doing any playing. Planning is a fairly simple activity where you review what you need to do, take on board your teacher's suggestions, and then work on all that in an organised fashion.

Another practice-related point is that "practice" like "science" is a blanket term that covers many different techniques and strategies you can employ to get better. You could do worse than buy and use Practiceopedia. It's aimed at kids but the points are just as valid for adults. I've used every technique in this book at one time or another over the past 15 years. I'd also suggest doing a bit of reading around the subject of practice - there are many books, articles, youtube videos covering the subject. I'm not going to make specific recommendations because I'd be here all night - just use your common sense and ask questions if you get stuck.

As far as guitar setup goes: This is one area classical players don't generally get involved in. You buy a guitar and there's very little else to do. You don't have to adjust the bridge or the saddle - that's the luthier's job. You'll need a basic guitar to get you off the ground (acoustic, nylon-strung - not steel strung or electric) and that guitar is probably going to sound like ass. Don't worry. Once you've done a bit of practice and you're ready to invest in something better if your teacher is amenable get them to come with you to the guitar shop when you buy your next guitar. I've done that with every guitar I bought except my first guitar and it's worked out nicely.

Good luck!

These are more about practice techniques than lesson plans, but really good and aimed at young student: Practiceopedia: The Big Book of Practice Help


And from memory this one is more aimed at the teacher: The Practice Revolution: Getting great results from the six days between lessons