Paul,
The best advice I can give is to start simple and wok your way up.
Each success will build confidence and you will learn something from every weave.
I find the easiest and most common mistake I make is to put threads in the wrong slot.
Usually it will be to put the thread that was supposed to go into slot 8 into slot 12, or something like that.
i.e. They go on the wrong side of the nearest slot with a number.
To help avoid that, I put numbers on all the slots, or at least every second or third one.
The next tip is to only weave when your head is in the right place.
I usually know within a few minutes if my concentration levels are right. If they are not, I get up and walk away.
Likewise, I usually only weave for an hour or so in a sitting. As soon as I start to get tired or lose concentration I get up and walk away.
There are no prizes for finishing fast, so just take your time.
Start out with small weaves so you can complete them in a reasonable time frame.
Likewise start out with single layer weaves.
One of the things about the internet is that you get to see the best the world has to offer.
But what you DON'T usually see is all the failures that occurred on the journey.
Try not to be disheartened if your first efforts are not as good as Doc Ski's.... Neither was his