There are many techniques for auditioning. First of all, it depends on the type of audition you are going up for. The four main types are; Stage or theatrical, film, TV and commercials. I would say that there are certain elements of the process however, that applies to all four. These are the techniques that I will attempt to cover for you.
Anyone who has read my article;
Acting Tips...To Be Or Not To Be Method Or technical that
Is The Question.

You found several ideas on building a character. Some of the tips will be applicable to your preparation for any audition as well. Especially the memorization exercise. For those who missed it, it bares repeating.
If you dedicate yourself, and put in the time, you will learn the art of "quick study"and land every part you're right for.

{Every day take 15 minutes and practice reading out load. It doesn't matter what you read from. Take 3 sentences and read them out load each time looking down for just a glance, before looking up and trying to say as much as you can remember. At first you'll probably be only able to memorize 5 or 6 words from the first sentence. But by the end of the 15 minutes, you should be able to shout out at least the first sentence and part of the second. Don't push yourself, or you'll get discouraged. Your goal is to eventually be able to after only about 5 minutes of memorization learn any 3 lines.}

Can you imagine how impressed a director will be when he sees you making all the right choices and barely glancing at the script. You'll nail that audition!

Even if you are good at memorization, I don't think it's wise to have a first audition without a script or side, though. On a callback you might be instructed to have the scene memorized. But that means the director must have liked whatever choices you've made during the initial tryout.
If you come to the first audition, with everything memorized, and you have made the wrong choice, the director will see it as a finished performance. They  will decide that although you might be a good actor, you're just not right for this role.

So choices are very important to not only the development of a character, but also the audition process. You need to choose who and what the character is about, and show the
casting person your commitment to that choice. Now if you have made the wrong choice, don't worry. As long as you have a piece of paper or book in your hand, you are still able
to take direction. They will see that you are an intelligent and creative actor, and direct you to the right choice, and let you read again. Remember, as long as you bring something to the table, they will always want to work with you. Directors are famous for asking an actor to:
DO IT AS IF...  Which brings us to our next exercise.

You can do this with or without your scene partner. It is more fun with a friend, but you can do this exercise to a monologue. It's very simple but extremely effective. After you have the scene or monologue down pat, try doing them  AS IF.

For example; You are playing a big executive that is up for a promotion. Your best friend and colleague meets you for drinks to celebrate. Do the scene AS IF you just found out you're getting fired. Or perhaps your spouse is cheating on you. Or do it as if your friend is the one getting the promotion. There are all kinds of DO IT AS IF scenarios. The key is to always do the scene or monologue as written. You are simply changing the circumstances, not the dialogue.

(Years ago I had a small role on WKRP In Cincinnati . Loni Anderson proved that she was not only beautiful, but a highly intelligent creative actress. I saw the director ask her to do a
scene AS IF at least six different ways, and she nailed it every time.)

Again, if you are diligent in your pursuit of perfection, you'll put in the time and practice this exercise. It will pay big dividends, I promise you. It will also help you master the art of improvisation.
Which brings us to my next tip.

Improvisation is one of the actor's greatest tool. If your class or group are not doing improves currently, you have to find a way to include them in creative process. This is very important; IMPROVES DON'T ALWAYS HAVE TO BE FUNNY.
The key to anything made up on the spot, is trust. Trust that
the scene will find itself. By that I mean don't force it. If someone says that they are your uncle and you were thinking brother, you have to make the transition to uncle. You can't say " no you'remybrother".Improves are fun as well as very enlightening. You might be surprised to learn the number of casting people and even directors that utilize improvisation.

I want to leave you with two extremely pertinent words;
DISAPPOINTMENT and REJECTION
Every actor must learn to live with these words. Some longer than others. Always remember not to take them personally. You might think that you are perfect for the part, but the casting person undoubtedly sees it differently.

{you're to tall, to short, to thin, to fat, not old enough, to old, the list goes on and on. My favorite pet peeve; you didn't get the role because their brother or sister, cousin, niece or nephew, friend of a friend, in other words nepotism,}
As long as you know in your gut that you have given your best reading, never let any of those outside interferences effect you. On the other hand, take advantage of everything you can. If you know someone in the business, for example, don't ever hesitate to use them. Remember, ultimately it's your talent that will get you the job.

I have more FREE advice and tips on acting at:

Blueprint to Acting

If your goal is to be a STAR, no one can help you. I was, along
with many of my colleagues, as good or in many cases better then the so called stars of my generation. All you can do is be the best actor or actress you can be. If all you want
is to be in local or community theater, be the best you can be. If however you want to be a professional, then you must try to work at your craft, even if you're not getting paid at the time for it. You will be surprised at the connections you'll meet if you are constantly in the game. If all you want is to be a film or TV actor for example, there are plenty of student films you can get involved with. You don't have to be strictly a stage actor or actress.

One last thing. Whatever road you choose to travel, it is essential that you have something or someone to provide financial backup. Don't play the old starving actor role! In these turbulent times you must not put yourself in such a precarious position.

Well I hope I have helped you. Remember, always have an open mind and listen to everyone, taking only that which can HELP YOU.